My Forecast For Today ( February 14 )

An 8:50 PM Update:  A brief break in Norton-Wise will give way to a meso-scale band of very heavy snow into the late evening-early overnight.  Roads remain very bad and travel is discouraged!!!  This snowband will overspread the area from northeast to southwest.

A Major Winter Storm Will Impact The Mountain Area From Sunday Into Tuesday With Significant Snow And Possible Mixed Precipitation Types To Rain

Target Snowfall of 6.0″ in Norton-Wise ( +/- ) 2″ Spread.  This implies 4″ to 8″ of snowfall will be possible.  This includes snow that falls up to the change on Monday and any additional snow that may fall following mix-rain into early Tuesday ( this final snowfall period is most favored in upper elevations ).  As noted below, just a couple degrees of temp change aloft could make a large difference in snowfall amounts.

The Bottom Line – A Major Winter Storm will begin impacting the mountain region later Sunday.  Snow will develop during mid-late afternoon-early evening and continue Sunday Night into Monday when mixed precipitation types to rain will become possible.

It should be noted that the outcome of this event may not be known until after the system develops.  Arctic air currently in place greatly increases uncertainty as to when a change from snow to other types occur, with only 1 degree Celsius above 850 MB on the NAM Model, as an example, making the difference between snow and some other type of precipitation from sunrise on Monday to early afternoon.  After 1 PM Monday there is some increase in confidence for a change to mixed precipitation and/or rain.  This is a forecast that will have to be updated through Sunday.

If the bulk of this event falls as snow it could be a crippling event for the mountain area.  If a change from snow to mixed types or rain occurs by Monday morning it will still be a significant snow but likely not crippling.  Please stay tuned for later updates.

Overnight Into Sunday Morning

Increasing mid-high clouds. NW-N winds decreasing and shifting easterly into morning.  MIN temperatures from -10 degrees below zero in colder valleys to around 10 degrees on exposed middle elevation mountain ridges.

*High mountain valleys in the High Knob Massif and other valleys with direct access to cold air drainage from deep snowpack have already dropped to around or below zero ( e.g., Norton to Coeburn valley corridor ).  MINS to around -10 below zero will occur before clouds increase enough to stop falls as winds remain relatively light beneath Arctic High Pressure.

This Afternoon

Lowering cloud bases with virga giving way to flurries and snow developing from top to bottom ( i.e., high elevations to valley floors over time ).  SSE winds increasing to 5-10 mph, with higher gusts possible, along mid elevation mountain ridges & plateaus.  SSE-SSW winds increasing to 15-25 mph, with higher gusts, along upper elevation mountain ridges.  Temperatures varying from mid 10s to middle 20s ( coldest at highest elevations ).  Wind chills in the single digits and 10s ( sub-zero in gusts along high crests ).

Tonight Into Monday Morning

Snow & blowing snow.  Heavy at times.  Possibly becoming mixed with sleet or freezing rain. SSE winds 5-15 mph, with higher gusts, on mid elevation mountain ridges-plateaus.  SSW-SW winds 15-25 mph, with higher gusts, along upper elevation mountain ridges.  Temps rising and becoming widespread in the 20s.  Wind chills in the 10s & 20s on exposed mid-upper elevation ridges & plateaus ( single digits in gusts along mid-upper elevation ridges ).

Weather Discussion ( February 13-14 )

Late Afternoon Update

The only changes this afternoon were to begin stronger winds earlier than I had forecast by tonight, with gusts exceeding 30 mph atop the High Knob Massif and Black Mountain already, and to lower temperatures a little.

Initial evaporative cooling has dropped temperatures across the area, with recent recovery only at highest elevations on strong southerly winds ( into mid 10s with sub-zero chills in gusts ).

Roads have become very slick across the mountain area.  Please do not travel unless absolutely necessary.

As of 4:00 PM temperatures were running around 6 degrees colder than forecast by the NAM Model for this time, so now it becomes a waiting game to see when warmer air aloft will change snow into mixed precipitation or dreaded freezing rain for places that remain below freezing.

Bowling Green in southern Kentucky recently changed from moderate-heavy snow to freezing rain at 28 degrees.  So we can not rule out a transition from snow to freezing rain, which I have added to the forecast for the period from tonight into Monday AM.

My forecast snowfall amounts will hold for now.  Stressing once again that lower end totals will be realized if a change to mix-rain occurs faster, while higher end tallies will occur the slower the transition from snow to mix and rain.  That is the main reason for the 4″ spread in most amounts, with the  ( + ) used for the potential that precip will be heavier than models have predicted and the change a little slower.

There will be a sharp cut-off in snowfall amounts south of the Tri-Cities, just off the edge of my snowfall map above, which will be south of the main isentropic lifting region ( where moisture is being transported up the sloping edge of retreating arctic air ).

A better idea of snowfall totals for this event will be had when the first 6-hour snow measurements are made by around 9:00 to 10:00 PM tonight.

My Overnight Discussion

Reference my 021316 Forecast discussion section for details on this past weather event, and a look at different model forecasts for the upcoming winter storm.

The main change to my forecast for tonight, which I made last night, is to drop MIN temperature well below zero for some of our mid-upper elevation mountain valleys which either have or have access to ( via cold air drainage ) deep snow which is helping to chill the air even more ( a general 6″ to 12″+ of snow depth is currently across northern slopes and high valley basins of the High Knob Massif, with lesser but still significant snow depths in other major mountain ranges of the area ).  I noted in my forecast last night that temps could become colder than I had if skies were clear.

Temperatures are currently around 0 degrees atop high mountain crest lines, and it is easy to see how lofty valleys have gotten so cold tonight ( this process occurring throughout the year on many nights favorable for cold air drainage, with enhancement during times with significant snow covering the ground ).

Although Black Mountain lacks high valleys, the sprawling and adjacent High Knob Massif is full of basins with many high valleys that sit between 2700 & 3500 feet above sea level.  When air that is already around 0 degrees drains over deep snowpack into a basin capable of collecting and holding it until vertical build up allows for spillage of air farther downstream, it can get very cold and drop well below summit temperatures.

The funneling downstream into mid-elevation valleys, such as that in which the City of Norton, Ramsey, Tacoma, and Coeburn rest, also pools and chills upon open valley floors ( the air being generally a little “milder” than in upper elevation valleys since there is more natural compressional warming with descent down from 3000-4000+ foot crestlines ).  Some micro-climatology that I have learned over the years, and hope to expand with help of my friends at the University Of Virginia’s College At Wise.

*The descent of air from upper elevations straight into lower elevations below 1500 feet, for example, appears to undergo enough compressional warming to offset much of the cooling.  Valley towns such as Harlan and Pineville, for example, tend to be much milder in low elevations below Black Mountain in SE Kentucky than towns on the Virginia side of the stateline during many nights conducive for cold air drainage.

 Even here in Clintwood, at my official NWS station, the air temperature has dropped to 5 degrees over only 2″ of snow depth and a much more limited vertical drainage basin in comparison to places like the City of Norton-Tacoma area.  This is a bitter night regardless of your location, but mid to high valleys ( especially ) with snow cover will be coldest!

Regardless of the time of year, or the specific weather setting, there are nearly always significant differences between lower, middle, and upper elevations.  A major objective of this website being to help educate about these differences, and at the same time provide a useful resource for those who live, work, travel, and yes, play, amid these diverse elevation zones.

Focus now shifts to a major winter storm system.

Regardless of how much snow falls, models have settled on this being a heavy precipitation event so the timing of the change from snow to mix-rain will be critical in dictating amounts where you live.

The European Model is predicting 1.70″ at the Wise gridpoint, same as the NAM Model above ( it predicts a total of 4″ of snow at 10:1 ).

While models continue to agree on a heavy axis of precip along the western side of the Appalachians, precise snow amounts are still somewhat varied.

The average of 5 different models for the Wise gridpoint is 4.8″ of total snowfall.  The 51-Member European Ensemble group had a mean of just under 6″ for Wise on the 12z run, with a few outliers going as high as a foot or more.

There is concern for significant orographic enhancement amid the High Knob Massif, where heavy precipitation is favored in a pattern like this ( whether it be snow or rain ).  With 6-12″ snow depths currently, the snow will be deep upon change to mix-rain.  Will the snowpack be able to retain water enough to prevent major run-off.

That is another concern to be considered as this winter storm event unfolds ( by later Monday into Tuesday ).

*With luck, upper elevations will change back to snow to halt or slow run-off before it gets out of hand into early hours of Tuesday.

Check back for Sunday Updates.

My Forecast For Today ( February 13 )

**A Major Winter Storm Will Impact The Area From Sunday Into Tuesday With Significant Snow & Possible Mixed Precipitation Types.  Scroll Down For Details.

The Bottom Line – A Major Winter Storm will begin impacting the mountain region Sunday.  Snow is likely to develop into the mid-day to early PM and continue Sunday Night, with hazardous conditions across the region due to bitterly cold temperatures expected into Sunday Morning.

The amount of total snowfall remains uncertain, but 4″ or more looks likely Sunday PM-Sunday Night as snow density initially begins low.  Stay tuned for updates on this developing winter storm setting.

My Previous ALERT

ALERT For Heavy Snow Squalls In Upslope Locations Tonight Into Saturday AM. Extremely Bad Conditions Are Expected To Develop Overnight As Temperatures Drop – Dangerous Cold Will Be In Place Through Saturday & Sunday Morning.

A band or broken line of intense snow squalls will impact the upslope side of the mountain area during the early to mid overnight period with near zero visibility in heavier squalls and hazardous road conditions.  Hit-miss squalls will continue to be possible into today.

Updated:  The Arctic Front snow arrived around 3 AM and produced 45 minutes of heavy-light snow at UVA-Wise and more than 1-hour of driving snow on High Knob ( where it was a horizontal-wind blown fall of snow ).  The lee side of a roof top gained more than 4″ between 8:12 PM and 4:27 AM, with numerous snow showers and wind driven squalls.

Some roads in the high country of the High Knob Massif may become impassible due to blowing & drifting snow into today.

Overnight Into Saturday Morning

Snow showers & squalls.  Whiteout conditions at times in squalls ( with hit-miss coverage ).  Winds NW-NNW at 10-20 mph, with higher gusts, along middle elevation mountain ridges & plateaus.  Winds NW 15-25 mph, with higher gusts, along upper elevation mountain ridges.  Becoming bitterly cold by morning.  Temperatures varying from 0 degrees at summit levels of the High Knob Massif to lower 10s ( single digits to 10 degrees in Norton-Wise ).  Wind chills from 0 to -10 degrees below zero on middle elevation mountain ridges and plateaus, with -10 to -30 degree below zero chill factors in upper elevations above 3000 feet.  Blowing-drifting snow along upper elevation ridges.

This Afternoon

A continued chance for flurries.  Bitterly cold.  NW-NNW winds 10 to 20 mph, with higher gusts, along mid-upper elevation ridges-plateaus.  Temperatures varying from  single digits at highest elevations in the High Knob Massif to middle to upper 10s, milder lee of the mountains toward the Tri-Cities.  Wind chills varying from 0 to -20 below zero in upper elevations to 5 above to -10 below zero along middle elevation ridges.

Tonight Into Sunday Morning

Increasing mid-high clouds. NW-N winds decreasing and shifting easterly into morning.  MIN temperatures 0 to 10 degrees ( colder if skies can clear completely for a period of time in places with snow cover ).

Weather Discussion ( February 12-13 )

My Afternoon Update

My update this afternoon features a look at the current forecast, snowfall during the past 24-hours, and what will the next winter storm bring?  No rest for the weary!

The only update to my previous forecast is to remove all but flurries, as a few continue northeast of Clintwood, and to raise the PM temperature ever so slightly.

True air temperatures, via official thermometers protected from snow glare, paved surfaces etc…will have a chance to reach into upper 10s for some along the upslope side of the mountains ( I had low-mid 10s ).  Lower elevation valleys will possibly crack 20 degrees ( a heat wave ), with milder conditions south of the mountains toward the Tri-Cities.

Highest elevations, especially those above deep snow and on north slopes in the High Knob Massif, will remain in single digits for the entire day ( despite sunshine ).

Snow glare over a general foot of snow atop the High Knob Massif, with large variations in depth from a wicked overnight period.

A general 2″ to 5″ of snow fell along the upslope side of the mountains during the past 24-hours, coming in at the bottom of my forecast range when including my spread potential which was listed in the forecast.

City of Norton Water Plant

February 12 at 3:00 PM
0.5″

February 12 at 9:00 PM
Trace

February 12 at 3:00 AM
1.0″

February 12 at 9:00 AM
1.3″

Snowfall Total: 2.8″
( 6″ Mean Snow Depth )

Snowfall measurements courtesy of Joe Carter & Wes Ward.

*The 3:00 AM total that fell in the Arctic Front snowband had to be partially estimated due to wind blowing the snow off snowboards.

Wes Ward measured 6″ of mean snow depth at the City of Norton Water Plant before sunrise, counting old snow, with Joe Carter measuring 1.3″ of new snowfall between 3 AM and 9 AM as snow showers and local squalls continued.

My friend Darlene Fields sends out a postcard view of the morning in High Chaparral of the High Knob Massif, with 3.5″ of new snowfall adding to old snow, as some is still falling when this photograph was taken at 9:00 AM.

New snowfall reached at least 5″ up at the summit level of the High Knob Massif, if not a little more, with wicked overnight conditions amid snow, blowing snow, and brutal wind chills.  Snowfall with the Clipper reached only 0.5″, so nearly all new snow came via NW Upslope Flow last night into this morning.

On the downslope side of the mountains, with respect to NW Flow, it was a different story with 1.5″ in Jonesville coming almost entirely with the Clipper.

Anna Hess reported much the same in The Pines of the Clinch River Valley, near Dungannon, where 0.8″ of snow fell ( a mere 0.2″ during the NW Flow period as moisture robbing along windward slopes of the massif stole it! ).

Major Winter Storm

These are from 7 AM Model Runs.

Turning focus toward the next major winter storm finds that models today are in rather amazing agreement with respect to total precipitation & axis of heaviest amounts.

I am not allowed to show the European Model, but it has a general 1.50″ to 2.10″ of total precipitation along and west of the High Knob Landform corridor ( similar to the NAM below but somewhat heavier in total amounts ).

The NAM Model group shows an axis of heaviest precip along the western side of the southern Appalachians.

This event is not yet fully in view of the high resolution NAM, but the trends in precipitation distribution are clear.

The GFS Model has an axis of the heaviest precipitation amounts along the High Knob Landform corridor and the Cumberland Plateau of middle-eastern Tennessee.

The Canadian Model ( GGEM ) is very similar, again with an axis of heaviest precip along the Cumberland Mountains and adjoining Cumberland Plateau ( above ).

The JMA Model ( Global Japanese ) also picks up on this same axis with SW-NE orientation in the southern Appalachians.

The Flow-following Finite-volume Icosahedral Model, called FIM9 for short ( which divides grids up using polyhedrons into mostly hexagons and 12 pentagons for the globe ) again shows this same type of SW-NE axis of heaviest precip along western slopes of the southern Appalachians.

In summary, as good of agreement as one ever sees from a set of models run for the same time ( 7 AM Run Saturday, February 13, 2016 ).  Actually, impressive.

As regards precipitation type, it is not as simple.

Model Snowfall Forecast’s From 12z Run

The European Model, which I am not allowed to show, predicts 6″ at the Wise gridpoint with up to 8″ in the area.

The NAM Model group is more varied, with 2.9″ to 5.3″ at the Wise gridpoint and locally up to 10″ on the NAM 4 KM ( but it does not extend through the entire event ).

The GFS Model ( below ) has 3.5″ at the Wise gridpoint with a MAX toward the southwest that goes up to more than 8″ .

The Canadian Model ( GGEM below ) predicts 5.1″ at the Wise gridpoint with a MAX also indicated toward the southwest.

The JMA ( Japanese ) snowfall forecast is not available.

The FIM9 14 KM Model shows again a snowfall max toward the southwest from Wise, centered across the High Knob Landform corridor.

 Initial Thoughts: A heavy precipitation event is coming from Sunday through Monday, with the amount of snowfall being the biggest unknown.

It is clear that all precipitation will begin as snow and continue that way through Sunday into early hours of Monday.  Since this is being driven by strong SW flow amid an “open wave” type of setting, it is worrisome since past climatology shows tendency for orographic enhancement along the High Knob Landform sector.  This actually seems to be picked up on by some of the models during these morning runs shown above.

Although the flow is not deeply SW, evaporative cooling amid a retreating arctic air mass is going to play a role in the temperature structure of this system.  If strong low level inversional conditions form, then strong SW winds can flow above with more limited vertical mixing ( that could keep low-levels colder during much of the event ).  

Since models such as the NAM show only limited warming above 850 MB it becomes problematic and could easily trend toward more of the precipitation falling as snow, especially amid the sector where SW air flow rises upward through the High Knob Landform corridor.

I will issue a preliminary snowfall forecast tonight.

The Bottom Line – A Major Winter Storm will begin impacting the mountain region Sunday.  Snow is likely to develop into the mid-day to early PM and continue Sunday Night, with hazardous conditions across the region due to bitterly cold temperatures expected into Sunday Morning.

The amount of total snowfall remains uncertain, but 4″ or more looks likely Sunday PM-Sunday Night as snow density initially begins low.  Stay tuned for updates on this developing winter storm setting.

My Early Overnight Discussion

Reference my 021216 Forecast for more weather details.

Snow showers started increasing during the evening and have been intermixed with squalls in a hit-miss fashion for any given location.  Low visibility has occurred in squalls.

Squalls along the actual Arctic Front at 850 MB, which has been followed through the previous evening, are now just northwest of Wise County and will deliver some intense snowfall to places where they strike.

Snowfall amounts are going to vary significantly across the area in this type of pattern, even though all locations along the upslope side of the mountains will have accumulation.

The increase in snow showers and squalls can clearly be seen via the connection to Lake Michigan, with limited activity at 7 PM ( above ) as the flow was passing north of southwest Virginia, then a dramatic increase along the upslope side of the mountains during the evening as the flow turned southward off Lake Michigan ( below ).

Squalls up to 1:30 AM have tended to hit repeatedly in some places with 1.5-2″ here at my station in Clintwood.  This may even out by morning, and if not then large differences in snow amounts will certainly occur over relatively short distances.

Temperatures are dropping with bitterly cold conditions along mid-upper elevation ridges already, well ahead of the coldest air that is still upstream of the mountains ( a plunge to come shortly after passage of the 850 MB Arctic Front ).

A Major Winter Storm is on tap for the mountain area beginning late Sunday and lasting into early Tuesday.  Details, are yet to be worked out; although, precip is looking to be very significant.  Figuring out how much falls as snow, frozen, rain is impossible at this point.  Lets hope the next 24-hours will bring more model agreement on storm track, intensity, amounts.

The JMA ( Japanese ) Model and Canadian Model have it as all snow, while the NAM, GFS, and European show significant snow to rain before a change back to snow.  But they differ significantly in the important details, such as track, which would greatly help if known for certain via past climatology of such storm tracks.

Have a safe Saturday.

My Forecast For Today ( February 12 )

ALERT For Accumulating Snow Developing Today With Heavy Snow In Upslope Locales Tonight Into Saturday.

Extremely Bad Conditions Are Expected To Develop As Temperatures Drop – Dangerous Cold Will Develop Late Friday Night Into Saturday-Sunday AM

With respect to the High Knob Landform corridor, the area within the yellow on my forecast graphic possesses the greatest uncertainty for snowfall totals, depending upon the Clipper track and amount of snow which can penetrate into the Powell River basin on NW flow.  The area possessing the highest certainty is upper elevations of the High Knob Massif where 4-8″ or locally more will be possible.

Target Snowfall of 4.5″ in Norton-Wise ( +/- ) 1.5″ spread potential.  This implies potential for 3″ to 6″ of snowfall in the Norton-Wise area, with locally heavier amounts likely in upper elevations of the High Knob Massif from today into Saturday Night.

A widespread general snowfall will develop today with a fast moving Alberta Clipper System.  The bulk of accumulation leeward of the Cumberland Mountains is expected with this system before NW Upslope Flow snow showers, squalls, and snowstreaks develop tonight into Saturday.  Due to recent bitter cold, travel conditions are expected to become hazardous across the region with an axis of heavier snow along and/or south of the High Knob Massif into the Great Valley of NE Tennessee with the Clipper.

Potential of a Major Winter Storm Is Increasing for  February 15-16.  Please stay tuned for updates.

Overnight Into Mid-Morning Friday

Increasing clouds with snow developing between sunrise and mid-morning ( especially along and south of a Harlan to Wise line ).  Winds becoming S-SW at 5-15 mph, with higher gusts, across mid to upper elevation mountain ridges and plateaus.  Temperatures in the 10s to low 20s, tending to rise some into morning.

Mid-Morning Through This Afternoon

A period of steady snow giving way to flurries and/or a brief break prior to snow showers increasing late within the upslope zone with respect to W-NW winds ( areas inside RED on my snowfall forecast graphic above ).  Winds becoming W-WNW at 5-15 mph, with higher gusts.  Temperatures varying from low 20s to low 30s ( coldest at highest elevations ).  Wind chills in the 10s and 20s.

An organized band of intense snow, with whiteout conditions, will become possible by the late evening-Midnight period with arrival and passage of an Arctic Front ( stay tuned for better timing ).

Tonight Into Saturday Morning

Snow showers & squalls.  Whiteout conditions at times in squalls ( with a hit-miss coverage ).  Winds becoming NW-NNW at 10-20 mph, with higher gusts.  Becoming bitterly cold by morning.  Temperatures varying from 0 degrees at summit levels of the High Knob Massif to lower 10s ( single digits to 10 degrees in Norton-Wise ) by morning.  Wind chills from 0 to -10 degrees below zero on middle elevation mountain ridges and plateaus, with -10 to -30 degree below zero chills in upper elevations above 3000 feet.

Blowing & drifting snow will develop tonight into Saturday at exposed middle to upper elevations.  Some roads in the high country of the High Knob Massif may become impassible.

Weather Discussion ( February 11-12 )

My Afternoon Update

No changes to my forecast this afternoon with everything being on track.  A general 0.5″ to 1″ of snow was reported with the clipper system this morning, with highest totals toward the south ( as figured ) where Big Stone Gap got more than the City of Norton ( Around 1″ verses 0.5″ ).

The most snow fell across southern locations south of the High Knob Massif in the Great Valley of NE Tennessee from Bristol southwest to Gatlinburg.

Orographic clouds are laying low across the High Knob Massif, waiting now for the bitter air to help generate the real snow.

There is sure a bounty of cold air poised to drop down.

Temperatures today have ended up colder than the models predicted, and right within my forecast range of lower 20s to lower 30s ( coldest at highest elevations ).

Temperatures have been hovering in the upper 20s ( LNP says 30 but all other available sites report upper 20s ) in Norton-Wise.

It is now merely a waiting period for Great Lake moisture to come south with the bitter air upstream of the mountains.

Timing on the Arctic Cold Front is a little slower on the latest high resolution NAM 4 KM Model, with it being near the VA-KY border by around 1:00 AM.  So some time from late evening into the early overnight period.  Increasingly severe conditions develop along and behind the Arctic Front into Saturday Morning.

Meanwhile, light snow and snow showers will be developing during the evening in advance of the Arctic Front.

Light snow is falling now, as the most sensitive mode of the Doppler is barely able to detect, in Clintwood at 4:37 PM.

My Overnight Discussion

The picture of the day highlights conditions atop the sprawling High Knob Massif as the first rays of sunshine broke through the low overcast on Thursday morning.

The view from UVA-Wise around the same time.

Thursday again featured colder than average conditions with PM MAXS varying from 28 degrees in Clintwood to around 18 degrees at the High Knob summit level.

Beautiful skies ended the day…

with a deep, settled snowpack atop the High Knob Massif.

Some serious winter is on tap for the mountain region through early next week, with it beginning today as an Alberta Clipper races southeast into a digging trough.

A general 1-3″ of snow fell upstream with the Clipper as it crossed Iowa, with 2.2″ at last report officially measured at the Des Moines NWS Office.  The snow was on the nose of a polar jetstreak.

Following the jetstreak downstream it is easy to see that the left front exit region zone of high altitude lifting will be moving into the Mountain Empire, with a bias toward the southern areas if model runs at 00z ( 7 PM Thursday ) are on target.

I am glad that the NWS Forecast Office in Morristown, Tn., expanded its Advisory to cover counties in the Great Valley  since conditions are likely to become hazardous.

The mean of past climatology of clippers tracking SE from the Iowa area is that snow density tends toward 20:1, which will especially be true in this case given arctic air. Echoes on Doppler will initially evaporate before reaching the surface as the lower levels remain relatively dry.

This will act over time to enhance cooling and work at offsetting some of the warm air transport aloft.  Since winds below 4000 feet are not predicted to be that strong, there is a good chance that low-level temperatures will end up being colder than models predict.  This being especially true since clear early evening skies have allowed for good temperature drops in valleys.  Much like what happened with the January 20 clipper system.

The main difference between this clipper and the one back in January is that it will be followed by an Arctic Front that has an excellent Great Lake connection.  This will CRANK snow showers and squalls along the upslope side of the southern-central Appalachians tonight into Saturday.

An organized band of intense snow squalls is likely to develop and move southeast into the windward side of the Cumberland Mountain Friday evening, with rough timing obtained by using the 850 MB Theta-E pattern forecast.

The Arctic Front should be amid the DARK BLUE band shown on the above Theta-E forecast chart, which would roughly place it at the Virginia-Kentucky border by 10:00 PM tonight.  Timing on this, of course, being subject to change since this front will be developing over time today as bitter air surges south from Canada.

While some snow showers and squalls may form in advance of the front, it will be along and behind the Arctic Boundary that conditions become increasingly severe overnight into Saturday morning on excellent NW Upslope flow.

The LSLM ( Limiting Streamline for Lake Moisture ) is forecast to be along and northeast of the Great Smokies, so the best snow squalls should develop along-northeast of the Smokies with very little snow southwest of this streamline ( e.g., SW portion of NC ).

If this streamline forecast verifies, the High Knob Massif is in a prime location where past climatology of MANY such events show heavy snow is a given ( with riming and enhanced orographics ).

Snow showers are likely to continue into Saturday Night along the upslope side of the mountains as the coldest air mass of this winter season grips the region.

With any clearing by Sunday Morning temperatures could drop well below ZERO.  The amount of clouds, snow showers-flurries into that time remains to be determined for upslope locations.

It will be at least another day before models can get a handle on a Major Winter Storm system that begins to impact the mountain area by late Sunday into Monday.

The Bottom Line…A Harsh Period of Winter Will Be Gripping The Mountain Empire From Tonight Thru This Weekend Into Early Next Week – Dangerously Cold Temperatures And Simply Hazardous Outdoor Conditions For Humans & Pets.  Please remain safe.

My Forecast For Today ( February 11 )

ALERT For Bitterly Cold Temperatures-Wind Chills Continues Into Today.  This Pattern Will Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.

Please Remain Alert For Hazardous Traveling Conditions As Well As Ice On Decks-Porches-Walks.

An Alert For Heavy Snow Squalls May Be Needed For Friday Night Into Saturday, With Significant Snow Accumulations Along And NW Of The High Knob Massif & The Tennessee Valley Divide that will tend to create very bad road conditions with plunging temps.

Bitterly cold conditions are expected Saturday into Sunday as part of the Polar Vortex gets stretched southward into the Great Lakes and NE USA ( in wake of major upper stratospheric warming ).

Potential of a Major Winter Storm Is Increasing for  February 15-16.  Please stay tuned for updates.

Overnight Into Thursday Morning

Mostly cloudy & bitter.  Light snow and snow showers.  Winds W-WNW 5-15 mph, with higher gusts, along middle elevation ridges & plateaus below 2700 ft.  WNW-NW winds 10-20 mph, with higher gusts, on upper elevation ridges.  Temperatures varying from 0 to 5 degrees at the highest elevations to lower 10s.  Wind chill factors varying from single digits to as cold as -10 to -20 below zero on upper elevation ridges.

Mid-Morning Through This Afternoon

Becoming mostly sunny.  Cold.  Light WNW-N winds at generally less than 10 mph.  Temperatures varying from middle to upper 10s at highest elevations to mid-upper 20s  ( a little milder in lower elevation valleys with little to no snow cover within portions of the Clinch, Powell, Holston river valleys toward the Tri-Cities ).

Tonight Into Friday Morning

Increasing clouds.  Winds becoming S-SW at 5-15 mph, with higher gusts, across mid-upper elevation mountain ridges and plateaus.  Temperatures in the 10s to low 20s, tending to rise at higher elevations into morning.

Some accumulating snow will be possible with a Clipper System during the day Friday, with heaviest snowfall likely to develop in NW Flow upslope locations Friday Night into Saturday.

Weather Discussion ( February 10-11 )

Reference my 021016 Forecast for details on snow accumulations which have varied from locally 1″ or less in portions of the Clinch and Powell river valleys up to 10-18″ across windward slopes and crest lines of the High Knob Massif.

The air is so cold that as long as any lower clouds are along upslope locations, especially windward sides of the great High Knob Massif, some flakes of snow will continue ( as have been observed this evening on Eagle Knob ).

Snow and low clouds broke just in time for sunset to be revealed in its glorious beauty above the snow covered mountain landscape.

Wednesday afternoon temperatures were bitter cold with widespread 10s across middle elevations and single digits amid upper elevations ( above 3000 feet ).  A few lower elevation valleys managed to break above 20 degrees.

Wind chills as cold as -10 below zero occurred at Nora 4 SSE.

Relative humidity remained high along windward slopes all day, with continuous light snow and heavier snow showers in localized hit-miss fashion ( for the snow showers ).

 Temperatures have actually been rising a little at highest elevations during the evening, but wind gusts have been increasing to generate chill factors between -15 and -20 degrees below zero along high mountain crest lines.

Generally, it appears that clouds will remain abundant along the upslope side of the mountains into this morning before finally giving way to clearing.

In fact, more light snow accumulations are likely along windward facing slopes within upper elevations of the  High Knob Massif overnight, with flurries and light snow amid lower-middle elevations having a chance to slicken a few roads that have cleared in Wise-Dickenson counties.

It will take very little to do that given current air temperatures.

The coldest air with this first arctic blast ( the axis of the 850 MB thermal MIN ) will begin to shift northeast of the mountain area by morning.

Focus now shifts to both a temporary stretching and southward extension of the Polar Vortex ( above ) and a very active upstream array of energy across the Pacific Ocean.

 Following a break today the pattern quickly turns active again with a Clipper System diving down into the base of another deepening USA trough Friday.

Light snow will spread across the region during the day Friday, in advance of another blast of bitter air arriving Friday Night into Saturday.  Along with this a Great Lake connected NW Flow period will crank up intense snow squalls along the upslope side of the mountains Friday Night into Saturday along-behind an Arctic Front.

My preliminary projection is for 1″ to 3″ of snow across the area in general, with 3″ to 6″ in favored upslope locations along and north  of the High Knob Massif & Tennessee Valley Divide ( generally the most being in upper elevations of the massif above 3000 feet ).  Stay tuned as I will make an actual forecast tomorrow night.

Models will require a couple more days before the details of a potentially major early week storm system can be figured out, with energy for this system still in the Pacific Ocean.

There is plenty enough ensemble support in the 51-Member European Model cluster to warrant that this will be one to closely watch and flag now for the potential of significant wintry precipitation.  Stay tuned.

Make it a great Thursday.

My Forecast For Today ( February 10 )

ALERT For Bitterly Cold Temperatures-Wind Chills Today Into Thursday AM.  This Pattern Will Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.

Please Remain Alert For Hazardous Traveling Conditions As Well As Ice On Decks-Porches-Walks.

Some additional light snow accumulations will be possible through today, with locally heavier amounts along windward slopes of the High Knob Massif & Black Mountain.  Much of the middle-upper elevations will again remain in 10s & single digits through today ( coldest conditions at the highest elevations ).

Potential for additional heavy snow is being monitored for the Friday-Saturday period with a Clipper System leading a Major Arctic Outbreak ( with Great Lake connected NW Upslope Flow Snowfall following the upper air disturbance & Arctic Front ).

Bitterly cold conditions are expected by Saturday into Sunday as part of the Polar Vortex gets stretched southward into the Great Lakes and NE USA.

Potential for a Major Winter Storm is being monitored for the period from late in this weekend into early next week.

Overnight Into Wednesday Morning

Light snow & snow showers.  Local bursts of heavier snow.  Bitter cold.  Winds W to NW at 5-15 mph, with higher gusts along mid to upper elevation mountain ridges & plateaus.  Blowing and drifting snow with riming at high elevations.  Temps from single digits at highest elevations to 10s in Norton-Wise ( milder in lower elevations toward the Tri-Cities ).  Wind chill factors in single digits above & below zero, except wind chills as low as -10 to -15 below zero at highest elevations.

This Afternoon

Mostly cloudy ( some hazy sunshine possible ) with a continued chance for light snow, flurries, and heavier local snow showers.  Bitter cold.  W to NW winds 10-20 mph with higher gusts.  Blowing snow on exposed mid-upper ridges.  Temperatures varying from the single digits at highest elevations to the mid 10s-low 20s, mildest at low elevations in the Clinch, Powell, Holston river valleys toward the Tri-Cities.  Wind chills in the single digits above and below zero, except -5 to -15 below along upper elevation ridges.

Tonight Into Thursday Morning

Mostly cloudy & bitter.  Chance of flurries & snow showers.  Winds W-WNW 5-15 mph, with higher gusts, along middle elevation ridges & plateaus below 2700 feet.  WNW winds 10-20 mph, with higher gusts, on upper elevation ridges.  Temperatures varying from 0 to 5 degrees at the highest elevations to lower 10s.  Wind chill factors varying from single digits to as cold as -10 to -20 below zero on upper elevation ridges.

Weather Discussion ( February 9-10 )

My Afternoon Update

The only update to my forecast for this afternoon was to increase wind speeds a little, and add blowing snow for the higher mountain ridges ( especially in upper elevations of the High Knob Massif where snow is deep ).

At 2:45 PM the air temperature was 6 degrees on Eagle Knob with wind chill factors as low as -15 degrees below zero.  The snowfall total had reached around 18.0″ at 3 PM with large variations in ground depths due to blowing-drifting and settlement.

Joe & Darlene Fields measured 2.5″ of new snow up to 9 AM Wednesday to bring the storm snowfall total to 12.7″ in the High Chaparral community of the High Knob Massif.  More snow has fallen & accumulated since that time.

Joe & Darlene Fields measured 0.5″ more at 4:00 PM to bring their storm snowfall total to 13.2″ in High Chaparral.  The mean snow depth was 8″ with a southern exposure there.

*They also lost 1″ of snow depth with melting on February 8 before the colder air and steady snow developed.  This illustrates why it is important to measure snowfall using the official method since the combination of many factors work to change ground depths.

If one had only looked at the 8″ depths observed at both the City of Norton Water Plant ( on a north slope ) and in High Chaparral ( south exposure ) it might be assumed that snowfall was the same.  However, by measuring the proper way it can be seen that snowfall was greater in High Chaparral than at the Norton Water Plant ( 3.5″ more in High Chaparral ).

There has been more drifting in the High Chaparral area, especially at more exposed sites and in higher elevations where more snow fell from Bowman Mountain to Little Mountain and the head of Big Cherry Lake basin ( but I’m just comparing points for illustration of how mere snow depth alone can be deceptive when not considering the big picture ).

Below is a look at conditions on Stone Mountain Road, up from Tacoma in Wise County ( State Route 706 ), at 1:00 PM this afternoon.  It is easy to see why school is closed in Wise County ( remember hundreds of folks live above 3000 feet along the Wise-Scott border area in the High Knob Massif as was well documented by Jessica Swinney in a 2008 study ).

Superintendent Andrew Greear reported 1.4″ of new snow accumulation at the City of Norton Water Plant between 9:00 AM and 3:00 PM today ( Wednesday, February 10 ).

This brings the official storm snowfall total to 9.7″, with around 8″ ( 7-8″ ) currently on the ground at this northern base of the High Knob Massif ( nearly twice this much has fallen at the summit level nearly 2000 vertical feet higher ).

This is a very accurate measurement and has followed the official NWS and University of Colorado Guidelines for measuring snow.

City of Norton Water Plant

February 8 at 10:00 PM
2.2″

February 9 at 4:00 AM
1.9″

February 9 at 9:00 AM
1.5″

February 9 at 3:00 PM
0.7″

February 9 at 9:00 PM
0.5″

February 10 at 3:30 AM
1.0″

February 10 at 9:00 AM
0.5″

February 10 at 3:00 PM
1.4″

Snowfall Total: 9.7″
( 7-8″ of Snow Depth )

*Snowfall measurements courtesy of Scott Craft, Andrew Greear, Caleb Ramsey, Wes Ward, and Joe Carter.

The water equivalent total has been around 0.50″ on nearly 10″ of snow ( 20:1 density ), with the density dropping during the second half of this event at the Norton Water Plant ( i.e., ratio of snow to water has been increasing as the air has turned bitter in Norton ).

This may not be the case atop the High Knob Massif, with only a snow core being able to reveal the results.  Past experiences where I have taken cores ( as recently as January 31 ) show that riming of snowflakes adds to the water content along with a tendency when air temperatures get around and below 10 degrees for the density of snow to naturally increase.  So the water content on 12-18″ of snowfall up above is likely significantly more than that obtained down in the City of Norton.

The High Knob Massif has been obscured in snow and clouds for days and is only now becoming partially visible along the horizon as moisture finally begins to decrease.

My Overnight Discussion

This active winter pattern is only going to get wilder in coming days, with multiple threats being watched from this current system through the weekend into early next week.

Wes Ward measured an additional 1.0″ of new snow at the City of Norton Water Plant at 3:30 AM to bring the current tally to 7.8″ ( with 6-7″ of settled snow depth ).

City of Norton Water Plant

February 8 at 10:00 PM
2.2″

February 9 at 4:00 AM
1.9″

February 9 at 9:00 AM
1.5″

February 9 at 3:00 PM
0.7″

February 9 at 9:00 PM
0.5″

February 10 at 3:30 AM
1.0″

Snowfall Total: 7.8″
( 7″ of Snow Depth )

*Snowfall measurements courtesy of Scott Craft, Andrew Greear, Caleb Ramsey & Wes Ward.

Reference my 020916 Forecast for details on earlier snow amounts.

Light snow which has never stopped falling along upslope sides of the mountains is picking up a little in intensity, with redevelopment of heavier localized snow showers and snowstreaks ( narrow bands of snow that follow along low to mid-level wind trajectories ), during the late evening-early overnight period.

This has been expected all along as the coldest 850 MB air is still to arrive, along with continuation of 700 MB moisture until early PM.  It will not be until mid-late this afternoon that some hazy sun can become more common, and due to very cold air remaining aloft, it could help develop a few heavier snow showers or narrow streaks.

With temperatures now so cold it will not take much snow to make even cleared roads slick, so please slow down and use extreme caution outside through today.

I like to use Nora 4 SSE observtions since it is a good calibrated site that is representative of middle elevations across the Norton-Wise & Sandy Ridge areas of Wise & Dickenson counties.

Tuesday temperatures remained in the 10s at most middle elevation sites across Wise & Dickenson counties, with upper single digits to around 10 degrees at the highest elevations in the High Knob Massif & Black Mountain.

Extensive riming has occurred in upper elevations of both the High Knob Massif and Black Mountain, with near saturated air through the afternoon amid bitter temperatures and snow.

A persistent and gusty W-NW wind has made conditions very bitter with chill factors between 0 and -15 degrees below zero along these high mountain crestlines.

This system has possessed abundant mid-level moisture and very cold air aloft that has enhanced instability.  Snowfall has been widespread across a wide region and varied in the accumulations due to a number of factors such as the prior warmth-rain of early February, low density snow that tends to settle and/or melt-sublimate faster than wet snow, and a W-NW flow which biases heaviest amounts to windward sides of major mountain barriers like the High Knob Massif.

Once again, this system lacks a Great Lake connected NW flow into the southern Appalachians.  Even though windward slopes & crests of the High Knob Massif have again done very well with snowfall, it would have been much heavier had the trajectory crossed the still open expanse of the Great Lakes.

An actual Great Lake connected NW Flow might finally develop by late week, along and behind an Arctic Front and upper air wave leading the way for a brutally cold mass of air that will be an actual part of the Polar Vortex that gets temporarily stretched southward in the immediate wake of a major upper stratospheric warming event.

Observe how a piece of the Polar Vortex temporarily breaks away from the main vortex center toward the Great Lakes and NE USA which will be the target of the most brutal air.

What happens just beyond this time into early next week will be a major concern for the Appalachians, with details still to be worked out by models as arctic air retreats.

Make it a great Wednesday.

My Forecast For Today ( February 9 )

ALERT For Accumulating Snow Tonight Into Thursday Morning With Bitterly Cold Temperatures-Wind Chills During Tuesday Into Thursday.  This Pattern Is Likely To Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.

Snow covered & hazardous road conditions will continue and worsen overnight into Tuesday morning as temps drop.  Travel is not recommended unless absolutely necessary.  Please use extreme caution if traveling overnight.

Overnight Into Tuesday Morning

Light snow, snow showers & bursts of heavy snow.  Turning bitter into morning.  W-WNW winds 5-15 mph, with higher gusts, at elevations below 2700 feet.  Winds W-NW 10-20 mph, with higher gusts, upper elevation mountain ridges.  Blowing & drifting snow at high elevations.  Temperatures dropping into low 10s at highest elevations and into upper 10s to lower-middle 20s at lower-middle elevations ( near 10 degrees at the summit of High Knob Massif ).  Wind chills dropping into single digits & 10s, except 0 to -15 below zero across upper elevations in the High Knob Massif & Black Mountain.  Extensive rime formation at high elevations.

This Afternoon

Light snow & snow showers.  Local bursts of heavier snow.  Cold.  Winds W to NW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges-plateaus ( blowing & drifting snow at exposed middle-high elevations, riming at high elevations ).  Temperatures varying from 10s above 3000 feet to lower-middle 20s ( milder in the Clinch, Powell, Holston river valleys toward the Tri-Cities ).  Wind chills in the single digits and 10s, with sub-zero values in gusts along high mountain crestlines.

Tonight Into Wednesday Morning

Snow & snow showers.  Local bursts of heavier snow.  Bitter.  Winds W to NW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges & plateaus.  Blowing and drifting snow with riming at high elevations.  Temps from single digits at highest elevations to the 10s in Norton-Wise ( milder in lower elevations toward the Tri-Cities ).  Wind chills in single digits above & below zero ( coldest at high elevations, with WCF’s as low as -10 to -15 below zero ).

New Snowfall – Tonight Thru Wednesday

A general 4″ to 8″+ along upslope side of mountains
( Target storm snowfall total of 8″ in Norton-Wise )

1″ to 4″ on downslope side of mountains

Target storm snowfall total ( for entire event ) remains at 8″ for Norton-Wise ( +/- ) 2″ to imply a potential for 6″ to 10″ .  A general 2″ to 3″ had accumulated up to Midnight on Feb 8 in Norton-Wise.

Target storm snowfall total ( for entire event ) is 8″ to 14″+ for upper elevations in the High Knob Massif.  A general 5″ to 6″ had fallen up to Midnight on February 8 at elevations above 3200 ft.

Snow depths at any given time, outside of drifting, are expected to be less than total snowfall by 1-3″ due to melting-sublimation and settlement over time during this prolonged event.  

Storm total extremes are expected to vary from more than 12″ amid highest elevations in the High Knob Massif to 3″ or less in portions of the Tennessee Valley ( downslope of mountains ).

This snowfall will occur over a prolonged period of time and generally be of low to very low density ( fluffy ).  This tends to enhance settlement over time as snow depth increases.  Note storm snowfall totals are between Monday AM and Thursday AM ( i.e., snowfall totals by Thursday Morning are currently projected to reach forecast storm total values ).

A prolonged rime event is expected for upper elevations, above 3300 feet, in the sprawling High Knob Massif where significant accumulations are likely during the next few days.

Weather Discussion ( February 8-9 )

My Afternoon Update

As of 9:00 AM, Superintendent Andrew Greear and Caleb Ramsey reported that total snowfall had reached 5.6″ at the City of Norton Water Plant ( 1.5″ of new snow accumulated during the 4:00 to 9:00 AM period ).

The official 8″-diameter National Weather Service rain gauge total reached 0.37″ for the water content on 5.6″ of snow, making for a 15:1 density ( snow to water ratio ) at the City of Norton WP.

3:00 PM Update:  Caleb Ramsey reported only 0.7″ of new snow at the Norton Water Plant at 3 PM.  This makes an event total of 6.3″ ( 6″ currently on the ground ).

Cody Blankenbecler reported 4″ of snow depth on East Park Avenue in downtown Norton, where some snow has melted, of course, along the pavement ( just after 4:30 PM ).

High above, on Eagle Knob of the High Knob Massif, around 2.0″ of new snow has accumulated to bring the storm tally to 13.0″ ( with moderate-heavy snow during the past hour ).

Joe & Darlene Fields confirm the new snowfall with 2.0″ of new snow reported in High Chaparral, to bring the storm tally to 10.2″ at their home ( elevation 3300 feet ) at 4 PM.

There have been some significant snow depth variations around Wise due to ground temperatures and wind in combination with this low density snow ( note I had anticipated that and have had it in my forecast during the past couple of days ).  The most snow being held on colder, north slopes and more sheltered locations.

At 9:30 AM, Joe & Darlene Fields reported a snowfall total of 8.2″ in High Chaparral of the High Knob Massif ( including 1″ which fell and melted during the day yesterday ).

The air temp on Eagle Knob has been hovering around 9 degrees this afternoon, with wind chill factors as low as -10 below zero at times in gusts on NW winds.  Snow is falling steadily and cloud bases have temporarily lifted off the summit to reveal extensive riming of trees.

At around the same time ( 9-10 AM ), the snowfall total on Eagle Knob of the High Knob Massif reached approximately 11.0″, with more than a foot of snow depth in many places.

By rather dramatic contrast, Chris Allgyer measured only 0.5″ on his deck in Big Stone Gap at 9:00 AM this morning.

Likewise, lee of the massif, in The Pines area of the Clinch River Valley near Dungannon, Anna Hess reported only 0.8″ of snow depth this morning.

To the north, here in Clintwood, I’d had 3.0″ of snowfall with a mean depth of 2″ on the ground.

My Overnight Discussion

As of Midnight, and the beginning of another day, snow depth reports varied from 1-2″ in Clintwood to around 3″ across Norton-Wise and 5″ to 6″+ amid upper elevations of the High Knob Massif ( above 3000 feet ).

4:00 AM Update: Scott Craft measured 1.9″ of new snow at the City of Norton Water Plant ( fell during 10 PM to 4 AM period ).  This makes  a storm snowfall total of 4.1″ and a depth of 4″ at the northern base of the High Knob Massif.

Scott Craft measured 2.2″ up to 10:00 PM on February 8.

Simply gorgeous scenes were captured around sunset.

The evening featured continuous snow with intervals of moderate to heavy snow.  Darlene Fields shows large flakes falling furiously in High Chaparral around 9:30 PM.

Roads in Wise became covered by around 11:00 PM.

Temperatures have been dropping with 10s across highest elevations ( wind chills around 0 degrees in gusts ).

There was some interest in thundersnow Monday.  When I was outside taking these photographs I heard a rumble that certainly sounded like thunder ( falling snow muffles sound waves and unless the thundersnow is close by it is difficult to hear from a distance ).  I have documented thundersnow many times in the High Knob Massif area.

There are several different ways, of course, to photograph snow falling.  One can set the shutter speed slow and have it silk out into streaks or set it fast to stop motion.  You can also set it intermediately, as I did above, for a little of both affects.

The above cross-section is taken along a line through the High Knob Massif area, from near the Ohio River in western Kentucky into central portions of North Carolina ( eastward of the Appalachians ).  Ideally, these cross sections should be taken perpendicular to the Thermal Wind in the mid troposphere, which I did approximately here since the 700-500 MB flow field was SW in nature early this morning ( the cross-section WNW-ESE ).

I have to first give credit to the late Dr. James T. Moore of Saint Louis University for teaching me about thundersnow following a major local event during March 1995 ( up to 15″ of snow depth accumulated atop the High Knob Massif  in a prolonged thundersnow event that lasted for hours ).

Dr. Moore was the king of Isentropic Analysis and a very kind man.  He was a true teacher and contributed greatly to the advance of meteorological science. 

The March 8, 1995 setting was much different from today but the principles are the same.  Conditional Symmetric Instability ( CSI ) is what one is looking for as during most thundersnow events clouds are not vertical.  The air mass may, in fact, be stable with respect to vertical ascent but is unstable with respect to slantwise motion.  Cloud tops may be less than 20,000 vertical feet tall but the convection can reach up to 40,000+ feet in a tilted or slantwise direction.

Such slantwise convective requires the slope of Momentum Surfaces ( which I have plotted above in brown ) to be more shallow ( less steep ) than the slope of Equivalent Potential Temperature ( called Theta-E ) Surfaces ( which I have in a green color above for the 7 AM Analysis on February 8 ).

The atmospheric state this morning featured a relatively large region with Potential Symmetric Instability since the air mass was not saturated within the layers in which I have roughly outlined ( in red ) where the requirements for CSI were present.  With forced lifting to saturation this state could have been converted into CSI, and ended up being in places with good lifting during the afternoon.  CSI is strictly defined only in a saturated environment with a lapse rate that is nearly moist-adiabatic in nature.

Approximately in the middle of the cross-section is an area where Theta-E decreases with height to indicate convective instability.  CSI & Convective Instability can co-exist, but the upright convection will typically dominate.

Focus during this 36-hour forecast cycle by short-range models are wanting to place the emphasis for heaviest snow across southern Ohio.

With abundant 700 MB moisture, cyclonic flow, and cold air advection into the mountains on W-NW flow it is difficult to not accumulate snow, at least at middle-upper elevations.

*Any time air is this cold aloft a RH of 70% or greater at 700 MB is significant, especially amid cyclonic flow.  It will be surprising if the upcoming day is void of snow showers and local squalls along the mountains.

All models have already greatly under-estimated snowfall in the High Knob Massif & Norton-Wise area up to this point in time, and are very likely also under-estimating snowfall through Wednesday.  So for now, I have kept my original  snow forecast numbers ( which are to Thursday AM ), and can update later today or tonight if needed.

While many always are interested in snow, the real deal upcoming is bitter cold that will intensify today into Wednesday ( temperatures during the daylight hours of Wednesday will struggle in the 10s in Wise and Norton ).  Longer days will help some, but this air mass and the next one upcoming by this weekend are of true arctic origin.  The actual Polar Vortex will be stretched enough to push the most bitter air of the entire winter season into the area by late Friday into Saturday ( followed by a potentially heavy snow ).

Make it a great Tuesday.

My Forecast For Today ( February 8 )

ALERT For Accumulating Snow Today Into Thursday Morning With Bitterly Cold Temperatures-Wind Chills During Tuesday Into Thursday.  This Pattern Is Likely To Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.

Although No Official Winter Storm Warning Has Been Issued For Wise County by MRX, Let There Be No Doubt That Conditions Tonight Into Tuesday Will Be Just As Bad Or Worse Than In Any Of The Tennessee Mountain Counties, That Currently Are Under A Warning, Amid The Norton-Wise & High Knob Massif Area

New high-resolution model runs are playing down the AM snow, via dry low-levels, despite a healthy looking Doppler to the west.  As noted in my weather discussion, models will struggle in this type of pattern on daily details.

A break in activity will be possible behind any morning snow before new development begins Monday afternoon.  Due to very cold air aloft, bursts of heavy snow ( amid general snowfall ) will be capable of producing whiteout conditions at times from this afternoon into Tuesday-Wednesday.  Increasingly bad conditions are expected as air turns bitterly cold Tuesday & Wednesday, with the worst conditions likely to develop along W-NW facing slopes and interior crests of the High Knob Massif & Black Mountain.

Overnight Into Mid-Morning

Increasing clouds into morning with a chance for a period of snow.  SSW to SW winds 5-15 mph, with higher gusts, along middle elevation ridges & plateaus below 2700 feet.  SW to WSW winds increasing to 10-20 mph, with higher gusts, along upper elevation mountain ridges above 2700 feet.  Temperatures mostly in the 20s to lower 30s.  Wind chills in the 10s & 20s ( coldest highest elevations ).

Mid-Morning Through Monday Afternoon

Any AM snow giving way to a break.  Then snow showers and snow squalls developing during the afternoon ( possible mixture at lower elevations, especially Russell Fork & Levisa Fork basins ).  SW winds shifting W at 5-15 mph, with higher gusts along mid-upper elevation ridges & plateaus.  Temps varying from 20s at highest elevations to the mid-upper 30s.  Wind chills in the 10s & 20s across upper elevations.

Tonight Into Tuesday Morning

Light snow, snow showers & bursts of heavy snow.  Turning bitter into morning.  W-WNW winds 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges & plateaus.  Temps dropping into low 10s at highest elevations and into upper 10s to low-mid 20s at lower-middle elevations.  Wind chills dropping into single digits & 10s, except 0 to -10 below zero at highest elevations in the High Knob Massif & Black Mountain.  Extensive rime formation at highest elevations.

Snowfall Forecast – Monday Through Thursday AM

A general 6″ to 12″+ along upslope side of mountains

3″ to 6″ on downslope side of mountains

Target snowfall of 8″ in Norton-Wise ( +/- ) 2″ Error Potential.   This implies a potential for 6″ to 10″ of snowfall.  Snow depths at any given time, outside of drifting, are expected to be less than total snowfall by 1-3″ due to melting-sublimation-settlement.  

Extreme snowfall totals are expected to vary from more than 12″ amid highest elevations in the High Knob Massif to 3″ or less in portions of the Tennessee Valley ( downslope of mountains ).

This snowfall will occur over a prolonged period of time and generally be of low to very low density ( fluffy ).  This tends to enhance settlement over time as snow depth increases.  Note snowfall totals are between Monday AM and Thursday AM ( i.e., snowfall totals by Thursday Morning are currently projected to reach forecast values ).

A prolonged rime event is expected for upper elevations, above 3300 feet, in the sprawling High Knob Massif where significant accumulations are likely during the next few days.

Stay tuned for updates on this preliminary forecast.

Weather Discussion ( February 8 )

My Afternoon Update

New model runs into the overnight were correct in playing down the morning snow, with no more than flurries as low level air remained dry.

No more than a dusting was on the ground atop the High Knob Massif at early afternoon.  That would soon change!

Whiteout conditions developed in the Norton-Wise, Sandy Ridge and High Knob Massif area amid wind driven snow.

The mountain landscape was quickly transformed into a wintry wonderland, but at the price of catching motorists who had not kept up with my forecast of blinding snow squalls off-guard.

This snow covered middle-upper elevations above 2000 feet, with sticking and melting to the northeast in lower elevations of the Russell Fork Basin ( Pound-Clintwood ).

Temperatures which spiked to 40 degrees amid the “break” into mid-day have now quickly dropped below freezing at all elevations above 2000 feet along and north of the High Knob Massif ( low 20s atop High Knob, with NW wind gusts to 30 mph generating WCFs down to around 5 degrees above zero at 4:00 PM amid riming ).

Focus now shifts to new convective bursts developing beneath bitterly cold air aloft to the west, with conditions expected to become extremely bad across the mountain area this evening into the overnight period in advance of a very compact vorticity max and excellent divergence ( diffluence of isobaric contours ) aloft ( the echoes across middle KY & middle TN will tend to intensify along the Cumberlands ).

Low-level temperatures will be dropping to enhance the bad conditions expected tonight into Tuesday morning.  Caution is advised for anyone planning to travel during this time.

Orographic pilatus clouds capping the high country of the High Knob Massif is a signal for enhanced snowfall ahead, via riming of snowflakes and increased volume of snow reaching the ground.

My Overnight Discussion

The main focus of this weather discussion is on a prolonged period of snowfall and increasingly cold air, starting today and continuing through this week into the weekend as a harsh period of winter settles into the Appalachians.

Reference my Extended Outlook for details on the big picture.

If my preliminary snowfall forecast numbers are not reached by Thursday morning, it is an excellent bet that they will be reached by Saturday afternoon ( February 13 ) as a strong reinforcing arctic blast brings more snow.  In fact, this preliminary snowfall forecast may certainly be too low by the time all is said and done.  Time will tell more and updates made as the actual weather pattern develops and new model data arrives in coming days.  Stay tuned.

*The latest European 16 KM Model is forecasting a general 6″ to 16″ of snowfall ( at 10:1 density ) along upslope sides of the mountains between this morning and Saturday afternoon ( February 13 ).

Due to very cold air aloft, the high-resolution NAM Model continues to repeatedly show very heavy local amounts as the atmosphere becomes absolutely unstable by this PM into Tuesday.  Placement of MAX amounts being varied on any given run, with the signal being most important to indicate intense bursts of snow ( whiteouts in blinding squalls ).

The GFS Model forecasts a general 2″ to 11″ of snow along the upslope side of the Appalachians between this morning and Thursday morning ( again, at 10:1 snow density ).

The GFS 5-day snowfall forecast is a general 6″ to 12″ along the upslope side of the Appalachians.

Regardless of how much snow falls, bitter cold air is going to become a major force in coming days with two distinct surges of arctic air into the Appalachians centered on the late Tuesday-Thursday period ( February 9-11 ) and the weekend ( Saturday-Sunday period of February 13-14 ).

The coldest temperatures will likely go sub-zero at some point during this period, and in the worst case scenario it would be possible that MAX temperatures in Norton-Wise will struggle to break above 0 degrees on the coldest day.  This is the potential which the pattern possesses, and only a notice for what could occur.  While this is not yet in my forecast, it has enough merit, given factors in my extended outlook and new model data, that it should be noted now to warn EMS personnel and residents well in advance.  If this does not happen, then we have dodged a very bitter bullet.

While the big picture of the pattern is relatively clear, details on any given day will be hard for models to fully resolve given the very cold air aloft and instability that develops vertically during the next few days.

Make it a good Monday.

My Forecast For Today ( February 7 )

ALERT For Accumulating Snow Monday-Wednesday With Bitter Cold Temperatures Tuesday-Wednesday

Abundant moisture will combine with very cold air aloft to produce snow, heavy at times, during a prolonged period beginning Monday and continuing through Wednesday.

Overnight Into Sunday Morning

Cloudy skies giving way to clearing into the predawn to morning hours.  Light SW winds shifting N at 5-10 mph on middle elevation ridges-plateaus below 2700 feet.  N winds 5-15 mph, with higher gusts, along upper elevation ridges.  Temps dropping mostly into the 20s ( variations from 10s in colder valleys, if skies clear during the predawn, to upper 20s-lower 30s along exposed mid-upper elevation ridges ).  Wind chills in the 10s & 20s ( coldest at highest elevations ).

Super Bowl Sunday Afternoon

Sunny with a chance for high clouds late.  N-WNW winds at generally less than 10 mph.  Temperatures varying from the lower-mid 30s in highest elevations of the High Knob Massif to the mid-upper 40s.

Tonight Into Monday Morning

Partly to mostly clear during the evening.  Increasing clouds overnight into morning with a chance for flurries and light snow developing.  SSW-SW winds 5-15 mph, with higher gusts, along mid elevation ridges & plateaus below 2700 feet.  SW-WSW winds increasing to 10-20 mph, with higher gusts, along upper elevation mountain ridges above 2700 feet.  Temperatures mostly in the 20s to lower 30s.  Wind chills in the 10s & 20s ( coldest highest elevations ).

The most significant snowfall accumulations Monday, during the period from 8:00 AM to 4:00 PM, are favored along and southwest of the High Knob Massif & Tennessee Valley Divide on SW Upslope Flow ( e.g., Norton-Wise & Sandy Ridge southwest to Big Stone Gap and Lee County verses lighter amounts from Pound-Clintwood to Haysi-Grundy where some mix may occur ).  Updates To Come.

Widespread snow, with embedded bursts of heavy ( whiteout ) snow will be possible from late Monday into Tuesday across the entire area, with heaviest amounts in general favoring W-NW facing slopes along the Cumberland Mountains and Blue Ridge.

Weather Discussion ( February 6-7 )

How would you like to photograph in a place where a bear uses an electrical pole as his scratching post?  To see more photographs reference The High Knob Landform website.

A seasonally cold Saturday was felt across the mountain area with morning MINS in the 10s, amid colder mountain valleys, and 20s along exposed ridges.  The afternoon was dominated by sunshine that gave way to high clouds with temperatures varying from near 30 degrees at summit levels of the High Knob Massif to upper 30s-mid 40s.

While snow may not yet be on the mountains, my friend Rodney Parsons submitted a great sunset view from the top of Stone Mountain in northern Lee County ( with some visible wave clouds to boot ).

Temperatures on this Super-Bowl Sunday will become a little milder than Saturday, but remain chilly, in advance  of a cold front that ushers in weather changes Monday.

Flow will be SSW-WSW in advance of a cold front from Monday morning through early-mid afternoon, which will tend to favor locations along and southwest of the High Knob Massif and TN Valley Divide for the most snow ( verses downslope locations in river basins of the Russell Fork and Levisa Fork ).

A key to this forecast, regardless of what model one looks at, is very cold air aloft and abundant moisture vertically by later Monday into Tuesday.  This supports widespread snow with embedded snow squalls ( bursts of heavy snow ) that could cause whiteout conditions at times.

*Temperatures aloft at around 17,000 feet are forecast to plunge into the -32 to -36 Celsius range ( -26 to -33 F below zero ) by late Monday into Tuesday.  This will generate steep lapse rates in the vertical ( i.e., rapid drops of temperature with increasing height ) and make the lower atmosphere unstable ( absolutely unstable with respect to air parcels ).

Past climatology of the High Knob Massif area shows that heavy snow tends to develop and fall when temperatures aloft become this cold with available moisture.  Otherwise, the flow trajectories are not shown to be from the Lakes on most models until beyond this period for the southern Appalachians ( the lake connected flow remaining from West Virginia northeastward along the mountain chain ).  This needs to be followed and updated on new forecasts.

If later Great Lake connected flow follows, either by mid-week and/or later by next weekend ( when the coldest air mass of the winter season potentially arrives ), this would add greatly to total snowfall amounts along the upslope side of the mountains with potential for very heavy totals in the High Knob Massif.

In a prolonged snowy period like upcoming, total snowfall amounts are likely to be greater than snow depths at any given point in time ( outside of drifting ) due to some melting-sublimation and settlement of snow.

The Bottom Line…A prolonged period of snowy and increasingly colder weather is upcoming this week from Monday through Wednesday-Thursday.  Bitter temperatures are likely during Tuesday-Thursday, with potential for a reinforcing blast of even colder air by this next weekend ( stay tuned for updates ).

**Reference my latest Extended Outlook for details.

Make it a great Super-Bowl Sunday.

My Forecast For Today ( February 5 )

Stream Levels Are Dropping But Will Remain Higher Than Normal On Steep Creeks Draining The High Knob Massif & On Mainstem Rivers Today

Overnight Into Mid-Morning

Flurries & light snow showers, then decreasing clouds into the morning.  NW winds 5 to 10 mph, with higher gusts, below 2700 feet.  NW-N winds 10-15 mph, with higher gusts, along mountain ridges above 2700-3000 feet.  Turning colder.  Temperatures dropping into the 10s to lower 20s, with lower to middle 10s at highest elevations.  Wind chills falling into the teens, except single digits above & below zero at highest elevations overnight into morning.  Any accumulations are expected to be light.

This Afternoon

Mostly sunny & chilly.  Light NNW-N winds.  Temperatures varying from the 20s across upper elevations to the lower to middle 30s ( milder in valleys of the Clinch, Powell, Holston rivers toward the Tri-Cities ).

Tonight Into Saturday Morning

Mostly clear.  Some high clouds possible overnight.  Colder.  N winds shifting SSE-SW at 5-10 mph on middle elevation mountain ridges & plateaus below 2700 feet.  Winds SW-W at 5-15 mph, with higher gusts, on ridges above 2700 feet.  Minimum temperatures ranging in the  20s across exposed mid-upper elevation ridges & plateaus, with 10s in colder mountain valleys ( with calm winds ).  Wind chill factors in the 10s on mountain ridges ( single digits to lower 10s at highest elevations ).

Weather Discussion ( February 4-5 )

A notable chill was in the Thursday air on northerly winds and abundant clouds.  It was plain cold in the High Knob Massif where I spent part of the afternoon.

Although water levels have come way down, it continues to gush on all creeks draining the High Knob Massif.  Caution is advised.

Temperatures remained below freezing all afternoon at the highest elevations, with mid 30s to around 40 degrees at lower to middle elevations north of the massif area.

Some flurries and light snow is falling during this early overnight from Clintwood to High Knob.  Accumulations, if any, are expected to be light ( as the forecast indicates ).

Although snow will not amount to much of anything, cold air is plentiful and making conditions feel like it is below zero degrees at summit levels of the High Knob Massif and Black Mountain during this early overnight ( in gusts ).

Temperatures are in the 20s in Norton-Wise & Clintwood.

Seasonably cold and mostly dry conditions will rule this weekend before snow and colder air begins to take over during early-middle portions of this coming week.

Stay tuned for details.

Have a great TGIF.

My Forecast For Today ( February 4 )

ALERT For High Stream Levels Along Steep Creeks Draining The High Knob Massif And On Mainstem Rivers.  Caution Is Advised Around All Streams.

Overnight Into This Morning

Mostly cloudy & colder.  Cloud bases obscuring highest elevations in freezing fog ( riming ), mainly above 3500 feet into morning.  Small chance of flurries.  SW winds shifting WNW to NNW at 5-15 mph, with higher gusts across mid-upper elevation mountain ridges.  Temperatures varying from lower 20s along upper elevation ridges to the upper 20s to lower 30s by sunrise to mid-morning ( milder amid valleys of the Clinch, Powell, Holston rivers ).  Wind chills in the 10s & 20s into morning ( coldest at highest elevations ).

This Afternoon

Partly to mostly cloudy.  Seasonably cold.  Light NW winds generally less than 10 mph.  Temperatures varying from upper 20s at highest elevations in the High Knob Massif to the upper 30s to lower 40s.  Wind chills in the 20s & 30s, except some upper 10s in gusts at highest elevations.

Tonight Into Friday Morning

Becoming cloudy with a chance for flurries and light snow showers.  NW winds 5 to 10 mph, with higher gusts, below 2700 feet.  NW-NNW winds 10-15 mph, with higher gusts, along mountain ridges above 2700-3000 feet ( low clouds with some riming possible at highest elevations ).  Colder.  Temperatures dropping into the 10s to lower 20s, with lower 10s at highest elevations.  Wind chills falling into teens, except single digits above & below zero at highest elevations overnight into morning.  Any accumulation varying from a dusting up to 1″ .

Weather Discussion ( February 3-4 )

Morning Update

My forecast is on track, with only slight changes for the afternoon and tonight.

Cloud bases have just been dragging across highest peaks through the morning with riming ( especially amid high gaps where air is accelerated upslope ).

Morning temperatures have varied from low-mid 20s atop the High Knob Massif and Black Mountain to lower 30s in Norton-Wise and along the adjacent ridge communities of Wise & Dickenson.

Low clouds are extensive, with a few breaks.  I have changed the afternoon wording slightly to reflect the potential of more clouds and added a dusting up to 1″ potential for tonight ( for upslope locations as a upper air disturbance crosses the mountains ).

Water levels remain high on steep creeks and mainstem rivers, so my Caution ALERT remains in effect today.

My Overnight Discussion

The main weather focus has been on heavy rain and strong rises on creeks and rivers during the past day.  Steep creeks draining the High Knob Massif continue to roar tonight but levels have peaked according to stream gauges.

The Big Stony Creek gauge is excellent to also judge levels on the South Fork of the Powell River, Little Stony Creek, and adjacent steep creeks in the massif.  The main exception being during the summer season when heavy rain events can be concentrated in local drainage basins ( and not extend across the entire massif ).  Any time water levels are within or above Yellow Alert stage the volume is significant and creeks roar ( a pounding roar develops when the level goes above Red Alert stage ).

The Clinch River, downstream of the massif, is forecast to crest during the morning to noon period today ( latest MRX projections being just below minor flood stage ).

Outside of heavy morning rains, Wednesday afternoon was very nice with temperatures becoming even milder than expected as low clouds broke relatively fast into mid-day.  An array of high-altitude clouds created a nice sunset.

Focus is now on a return to seasonably cold conditions with mainly dry weather during the next few days.  An upper air disturbance will be pushing across the mountains Thursday evening with limited moisture.  Some flurries and/or snow showers will be possible as air turns colder than today.  Any accumulations currently look to be light as streamlines will be from mid-continent and lack a good moisture source.

*A chance exists for wave development over the western NC area, with movement to and off the Atlantic Coast.  Any snow along the mountains currently looks limited late tonight into Friday, but this will be something to follow on new forecast model runs.

The shift back into cold air is well underway now across the high country, on NW upslope flow and increasing low level moisture, and should bring cloud bases down onto highest crestlines from the High Knob Massif to Black Mountain.

Temperatures have now dropped below freezing along highest crest lines, with gust chill factors in the 10s, on NW-NNW winds.

Bitter air and prospects for snow increase into next week but forecast models have much work to do in order to figure out a complex pattern featuring several jet streams and a array of embedded disturbances.  Axes of main snowfall currently vary from along the mountains to the Atlantic Coast ( from South Carolina to north of the VA Capes ).  Perhaps it will be both, but time will soon tell more.

For a review of recent winter photographs reference this section of the High Knob Landform website ( more to come in days ahead ).

Have a great Thursday.