Mountain Area Forecast ( Jan 10-12 )

An ALERT Continues For Strong SSW-SW Winds Into Thursday, With Strongest Winds Expected At Middle To Upper Elevations During Much Of This Period.

A prolonged period of very windy conditions, with high wind gusts, will be impacting the Cumberland Mountains during the Tuesday to Thursday period ( January 10-12 ).  Despite milder air working into the area, these strong winds will continue to make conditions feel cold Tuesday & chilly through Wednesday.  The strongest winds are expected to come in waves, centered on the daylight and evening hours of Tuesday as well as the Wednesday afternoon into Thursday time period.

**As moisture increases dense fog will become widespread at the highest elevations.  This will also need to be watched for at middle and lower elevations, especially within the SW Upslope Flow zone from Wise-Sandy Ridge plateaus southwest across the High Knob Massif into portions of Lee County ( and locally in other locations ) during the Wednesday-Thursday period.

Tuesday Night Into Wednesday Morning

Cloudy & windy.  A chance of evening showers, then rain developing into the overnight.  Wind driven across higher elevations.  Local downpours in the SW upslope zone.  SSW to SW winds 10-25 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  SSW-SW winds 20-35 mph, with higher gusts, along mountain ridges above 2700 feet.  A period of lower wind speeds into predawn hours ( then increasing again after sunrise ).  Temperatures mainly in the 30s to lower-middle 40s.  Wind chills in the 20s & 30s, except 10s highest ridges ( evening ).  Areas of dense fog developing into the overnight-morning.

*As milder, moist air comes into contact with cold, frozen ground the potential for dense fog formation will arise by the overnight-Wednesday period.  Dense fog formation is also more likely within the SW upslope flow zone where air is forced to naturally rise.  Caution Is Advised.

Wednesday Afternoon

 Windy with showers likely.  Downpours possible.  Areas of dense fog, especially in the SW air flow upslope zone.  S-SW winds 10-25 mph, with higher gusts, on mountain ridges and plateaus below 2700 feet.  Winds SW 20-35 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps widespread in the lower 40s to low 50s ( warmest at the lower elevations in the downslope zone from Pound to Clintwood, Haysi & Grundy ).

Wednesday Night Into Thursday Morning

Chance of showers & drizzle.  Areas of dense fog.  Windy.  SSW-SW winds 10-25 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet.  SW winds 20-35 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures widespread in the 40s.

A mild & wet pattern is expected during the next 5-10 days, with a heavy rainfall potential continuing to be monitored for next week.  Stay tuned for updates.

Weather Discussion ( Windy-Wet )

Wednesday Afternoon Update

Following a very windy Tuesday, with cold wind chills, a boundary that produced showers, local downpours, and light rain-fog changed wind directions and temporarily reduced wind speeds for a more pleasant Wednesday PM. Cloud bases even lifted briefly off all but highest peaks.

Cloud bases are lowering and winds are increasing once again as the sun is setting on this Wednesday.

Temperatures reached lower 50s at UVA-Wise through 4:00 PM, with low-middle 40s observed in upper elevations where a morning period featured wind speeds mostly under 25 mph.  This as the strongest winds are coming in waves, as predicted, with the next period of ROARING winds already underway at higher elevations.

*The warming nature of the atmosphere can be seen as temps at high elevations are just reaching their highest levels now, as the sun is setting ( the warmest temps observed since January 3 ).

Due to another period with a tightening pressure gradient I will keep my ALERT for strong S to SW winds into Thursday for middle-upper elevations of the Cumberland Mountains.  Many limbs have been blown out, so caution is advised. 

Previous Discussion

In my opinion it was a cold Tuesday. Even though temps are rising WIND was a major factor at middle-upper elevations amid the Cumberland Mountains, with 15-30 MPH sustained speeds from Wise upward in elevation ( gusts 40-50+ mph at higher elevations within the High Knob Massif, Black-Pine mountains ).  That made conditions feels like 20s-30s in Wise and 10s & 20s at upper elevations above 3000 feet.

Wind chills have consistently been in the 20s and 30s throughout Tuesday in Wise, even with Lonesome Pine Airport’s 1-2 degree F warm bias ( versus UVA-Wise and other local thermometers ).

Wind speeds only get stronger the higher in elevation you venture.

At 5:00 PM temperatures were the warmest of the day at highest elevations, and the warmest since last week, with low-mid 30s at upper elevations from the High Knob Massif to Black Mountain.

Snow remains solid, significant, and roads partially or completely covered in upper elevations of the High Knob Massif where winds sound like a JET taking off.  I still have some doubts if I will be able to take my Field Studies In Microclimatology class on a field trip into upper elevations by this weekend!  Time will tell.

Although a boundary with colder air will bear watching by Friday into this weekend ( first along western slopes of the Appalachians then down along the eastern slopes ) a much warmer pattern is clearly going to dominate most of the USA during the next 5-10 days.  This will also be a wetter pattern, with amounts needing to be monitored over time.

Periods of rain are expected, as many waves moves across the region amid fast flow aloft.  Due to the combination of both Pacific Ocean moisture ( at mid-high altitudes ) and Gulf of Mexico moisture ( at low-levels ) amounts over time could become significant.  This is what the synoptic pattern is saying versus any particular model.  Stay tuned.

The mean temperature during the next week to 10+ days will average well above “normal” for this time of year.

There are longer range signs, with expected changes within the stratosphere, that suggest a wintry pattern will return by late January into February.  More harsh weather ahead?  Time will tell amid a winter season that can not yet lock down into any given temperature regime, with wetness being the only consistent theme.

Mountain Area Forecast ( January 7-10 )

An Alert For ROARING SW Winds In Effect From The Overnight-Predawn Hours Of Tuesday Into Thursday, With Strongest Winds Expected At Middle To Upper Elevations During Much Of This Period.

**Blowing snow from the ground will be a factor overnight into Tuesday, especially at highest elevations.  Some roads will be covered in places which had previously been plowed.

A prolonged period of very windy conditions, with high wind gusts, will be impacting the Cumberland Mountains during the Tuesday to Thursday period ( January 10-12 ).  Despite milder air working into the area, these strong winds will continue to make conditions feel cold Tuesday & chilly through Wednesday.  The strongest winds are expected to come in waves, centered on the daylight and evening hours of Tuesday as well as the Wednesday afternoon into Thursday time period.  Stay tuned for updates.

Dense fog development, with wind driven rains, will also occur Tuesday Night into Wednesday, especially in locations along and southwest of the High Knob Massif & Tennessee Valley Divide.  Rain amounts of 0.50″ to 1.00″+ are expected in the SW upslope flow corridor of the High Knob Landform through Wednesday afternoon ( with added run-off from melting snow ).

*Due to frozen ground and melting snow fog development could become very dense in places and more widespread in coverage than just the upslope flow corridor ( i.e., the Sandy Ridge, Norton-Wise, High Knob Massif & Lee County zone ) as moisture increases by late Tuesday into Wednesday.

ALERT For Bitter Cold Air And Wind Chills Continues Into Sunday – Bitter Air Persisting Into Monday AM – Along With Hazardous Secondary Roads.

Bitter cold will grip the mountain landscape into Sunday.  Wind chills will continue to make bitter temperatures dangerously cold along middle to upper elevation mountain ridges, with 0 to -20+ degree below zero chill factors ( coldest along highest ridges ).

Sunday Night Into Monday Morning will offer the best conditions for extreme temperatures in mountain valleys, with diminishing evening winds.  Temperatures may again plunge to below zero in the colder mountain valleys.  I expect a large vertical temperature spread to develop into the overnight-Monday Morning as SSW-SW winds begin increasing again along higher mountain ridges ( with 20-30+ degree temperature differences between valleys and ridges becoming possible ).  The factor that may limit temperature falls being an increase in mid-high altitude clouds which may help off-set some of the radiational cooling & cold air drainage effects.

Updated: Overnight Into Sunday Morning

Increasing clouds.  Flurries and snow showers developing,  especially along and north to northwest of the High Knob Massif-Tennessee Valley Divide ( on the upslope side of the mountains ).  New snow accumulations of a dusting up to locally 0.5″ to 1.5″ .  Bitter Cold.  NW-N winds 5-15 mph, with higher gusts, on middle to upper elevation mountain ridges.  Temps varying from 5 degrees above zero to -5 below zero, except colder in any snow covered valleys that can develop calm winds.  Wind chill factors of 0 to -10 degrees below zero on middle elevation ridges, with -10 to -25 degree below zero wind chills upper elevation ridges.

Sunday Afternoon

Mostly sunny.  Some increasing high clouds possible late.  Bitter cold.  Light WNW-NW winds.  Temperatures varying from around 10 degrees at highest elevations to the upper 10s to around 20 degrees.  Wind chills below zero in gusts at the highest elevations.

Sunday Night Into Monday Morning

A rapid evening temperature drop, especially in mountain valleys.  Bitter.  Increasing high altitude clouds.  SSW-SW winds developing at 5-15 mph, with higher gusts, during the overnight-morning along higher mountain ridges. A large vertical temperature spread developing with variations from below zero in the colder mountain valleys to readings rising through the 10s into the lower 20s along exposed mountain ridges.

Monday Afternoon

Mid-high altitude clouds.  Becoming windy.  SSW-SW winds 10-20 mph, with higher gusts, below 2700 feet.  Winds SW-WSW 15-25 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures in the 20s to lower 30s, mildest in downslope locations from Pound to Grundy.

Monday Night Into Tuesday Morning

Mostly cloudy.  Windy.  SSW-SW winds 10-25 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet.  Winds SW 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from near 20 degrees to lower 30s.  Wind chills in the 10s to lower 20s, except single digits along high mountain ridges.

ROARING SW winds will continue and increase Tuesday, with a chance for rain showers developing.  Wind gusts of 30-50+ mph are expected in the Cumberland Mountains.

A wet and generally mild pattern, with a heavy rainfall potential, is being monitored for later next week into next weekend during the January 12-17 period.  Stay tuned for updates. 

Weather Discussion ( Bitter Cold )

Early Monday Update

Following a new dusting of snow ( up to 0.5″ on High Knob ) into early Sunday the second half of this weekend turned mostly sunny but remained very cold ( as expected ).

Sunday afternoon temperatures struggled toward 10 degrees atop the High Knob Massif and finally reached 19 degrees in Clintwood.  Better than Saturday MAXS, with Joe Carter of the City of Norton Water Plant recording a Saturday HIGH temp of just 14 degrees.  Maximums remained in single digits, of course, atop the massif.

High clouds late Sunday held off long enough to allow colder mountain valleys to plunge below 0 degrees into Sunday evening ( well below zero in high valleys ), with a “balmy” 1.7 degrees being the MIN at lower elevations in Clintwood prior to some rise with increasing clouds.

Winds will be increasing into Monday morning at high elevations, then mixing downward over time into middle and lower elevations.  By Monday Night, and especially Tuesday-Wednesday, SSW-SW winds are going to ROAR.  This will keep conditions feeling cold through Tuesday.

Previous Discussion

*Note: Due to current satellite trends and the latest model trajectories I have added redevelopment of clouds with a chance for flurries and snow showers into the overnight and Sunday morning.  New snow accumulations from a dusting up to locally 0.5″ to 1″ of fluffy snow will also be possible along the upslope side of the mountains, mainly over and north to northwest of the High Knob Massif and Tennessee Valley Divide.

Reference My 010617 Forecast for previous forecast details.

Reference My High Country Focus for information on 2016.

Reference The High Knob Landform for recent work & photos.

Bitterly cold conditions are the now the main weather factor, along with hazardous secondary roads, in wake of the first widespread winter storm impact of the season.

Storm Event Snowfall Reports For Jan 6-7
( Snow Depths On Morning of January 7 )

Clintwood NWS Station
4.6″ of Total Snowfall
( 4″ ground depth )

UVA-Wise NWS Station
4.7″ Of Total Snowfall
( 5″ ground depth )

City of Norton Water Plant
5.0″ of Total Snowfall
( 4-5″ ground depth )

Nora 4 SSE on Long Ridge
5.3″ of Total Snowfall
( 5″ ground depth )

High Chaparral of High Knob Massif
5.5″ of Total Snowfall
( 3″ to 6″+ depths )

Eagle Knob of High Knob Massif
6.5″ of Total Snowfall
( 4″ to 8″+ depths )

Wind did not become a factor in this event until the overnight-morning hours of Saturday, when increasingly gusty N winds developed across middle to upper elevations.  This helped reduce differences in total snow amounts between low-high elevations.

Temperatures tonight into Sunday Morning are very, very problematic, not due to the cold, but from a forecasting perspective since they are primed and ready to TANK.

Anyone watching me do this forecast live, during the past 1-2 hours can gather that this ( to me ) is the most difficult forecast setting there is ( outside of precip in marginal vertical columns ).  Enough high resolution data has now been collected during the High Knob Massif project at UVA-Wise, in combination with my decades of previous research in these mountains, to understand fully how delicate this setting is with UP and DOWN fluctuations in valley temperatures being typical as winds begin decoupling, then recouple and decouple, etc…it is amazing at times to both experience in person and to also follow with collected data.

*NOTE – Since I originally wrote this the forecast has been simplified by a trajectory from the Great Lakes which will allow for upslope clouds and flurries-snow showers to form into the overnight-Sunday Morning ( January 8 ).  Prior to this the trajectories were shown to just miss the area.  The best valley temp drops are now expected Sunday evening.

*With temperatures at 7:30 PM Saturday hovering around 0 degrees along high mountain ridges it does not take a rocket scientist to figure out that adjacent high valleys could tank if their winds diminish.  Especially given incoming dry air associated with High Pressure.  The key factor will be if the pressure gradient between High and Low pressure can relax by the predawn and morning hours of Sunday ( MINS could occur after sunrise  into mid-morning should that happen ).

Under these type of conditions it only takes a few hours for the literal bottom to drop out of temperatures, so I initially opened up the temperature range in my forecast to account for this.  Then I decided to just note it here, since so many factors are working against complete PBL decoupling in even deep valleys.

A check of the latest NAM Model shows that the local mountains will be close to Great Lake moisture advection  by overnight into Sunday AM, enough to reform upslope clouds, flurries and some snow showers along windward slopes.  So for these reasons, in combo with the pressure gradient, I have decided to hold temps in the 5 above to -5 below range  ( the potential for -10 to -15 below in mountain valleys is certainly there, but likely not to be realized on this night…another shot for it comes Sunday Night ).

While the wind field becomes very favorable for valleys to decouple by Sunday Night, an increase in mid-high clouds may then be the factor to keep the full cooling potential from being realized.  Stay tuned for later updates.

Mountain Area Forecast ( January 6-8 )

ALERT For Periods Of Snow Friday Into Saturday Morning With Widespread Hazardous Travel

ALERT For Bitterly Cold Conditions Friday Into Sunday

Overnight Into Friday Morning

Light snow & flurries.  Winds WNW-NNW at 5-15 mph, with higher gusts.  Temperatures dropping into 10s to around 20 degrees ( as cold as 10 degrees at highest elevations ).  Wind chills in the single digits and 10s, except below zero in gusts along upper elevation mountain ridges.  Rime formation in upper elevations.

Friday Afternoon

Periods of snow and flurries.  Bitterly cold.  Winds NW to N at 5-10 mph.  Temps  varying from lower-mid 10s in upper elevations to lower-middle 20s.  Wind chill factors in single digits & 10s ( coldest at highest elevations ).

Updated Snowfall Forecast: Friday Into Saturday

A general 1″ to 4″ of new snowfall is expected, with locally heavier totals in upper elevations of the High Knob Massif.  My target has been changed to the expected snow depth in the Norton-Wise area by Saturday, and has only been adjusted to account for new snowfall.

Target Snow Depth 5″ In Norton-Wise ( +/- ) 1″ Error Potential.  This suggests a possible range from 4″ to 6″ in Norton-Wise by Saturday ( this includes snow that fell through Thursday ).  Deeper depths will be possible in the High Knob Massif ( above 2700 feet ).

New snowfall Friday into Saturday will tend to be less toward the north, in places that received the most snow through Thursday, and greater toward the south from Norton-Wise into the High Knob Massif and adjacent Great Valley region.

Friday Night Into Saturday Morning

Periods of snow & snow showers.  Heavy at times.  Bitterly cold.  NNW-N winds 5-15 mph, with higher gusts on middle to upper elevation mountain ridges.  Temperatures varying from 0 to 12 degrees.  Wind chills from 5 above to -10 below, except -10 to -20 degrees below zero upper elevation ridges.

Saturday Afternoon

Snow showers and flurries ending.  Partial clearing possible by late PM.  Bitterly cold.  NW winds 5-15 mph, with higher gusts.  Temperatures varying from single digits within the upper elevations to 10s across lower-middle elevations.  Wind chills in the single digits above and below zero.

Saturday Night Into Sunday Morning

Mostly clear.  Bitter.  NW winds 5-15 mph along upper elevation mountain ridges.  Diminishing winds in valleys.  Temperatures varying from 5 above to -5 degrees below zero, except locally colder in mountain valleys.

Weather Discussion ( Harsh Weather )

Friday Afternoon Update

My only change is to ease the expected snow depth up a little from Norton-Wise southeast across the High Knob Massif as snowfall tonight becomes moderate to heavy before tapering to upslope snow showers & flurries.

I already had the coldest forecast of any sources, and if anything it may be even colder than I have predicted.

Around 2″ of snow is now on the ground across the Norton-Wise area, with 2-3″ in upper elevations of the High Knob Massif where significant rime has transformed the landscape into a winter wonderland amid bitter air.

A total of 2.1″ of snow was reported by Caleb Ramsey at the City of Norton Water Plant ( 2″ on the ground ) around 5:00 PM.

A total of 2.0″ has been measured in Clintwood, with locally more across northern Dickenson County ( mainly from Thursday ).

This air mass along the western side of the mountain chain is bitterly cold, with 4:30 to 5:00 PM temperatures varying from 10 degrees on Eagle Knob of the High Knob Massif and 11 degrees ( 10.6 ) on Black Mountain to 16 degrees on Sandy Ridge and 17 to 19 degrees in Norton-Wise.

Air will turned even colder into Saturday as temperatures plung toward 0 degrees at the top of the high country and to single digits to around 10 degrees at elevations of Norton-Wise and Sandy Ridge ( low-mid 10s at lower elevations ).

Temperatures during the day Saturday will remain in single digits at upper elevations and the 10s in Norton-Wise and in most of the Cumberland Mountains ( wind chills will make conditions feel even colder ).

The focus now turns to a final round of snow that is likely to become heaviest from the High Knob Massif area south and southeast.  This should push ground depths into my forecast range for Norton-Wise, and could exceed them if upslope on northerly flow becomes more of a factor with low density snowfall than models are currently indicating.

New snow accumulations tonight are likely up to along the VA-KY stateline, as past climatology of these events dictate, with a rapid diminishing of snowfall northwest of Pine Mountain and a notable gradient across the High Knob Massif area as upsloping N winds increase into the overnight and Saturday morning ( increasing amounts across the high country toward Norton-Wise ).

Travel tonight into Saturday is discouraged as bitterly cold air & snow will combine to generate widespread  hazardous travel conditions.

Previous Discussion

Reference My 010417 Forecast for previous details.

Air is turning bitter with more periods of snow upcoming into Saturday.  Places that received the most snow during Thursday, with 1-2″ in Clintwood and as much as 2″ to 5″ from John Flannagan Lake & Breaks Interstate Park into portions of Pike County, Ky., will tend to get the least.

Locations toward the south will get the most snow through Friday Night into Saturday, from Norton-Wise and the high country of the High Knob Massif southeast toward the TN-NC border and Great Valley ( where very little to no snow accumulated through Thursday Night ).

The track and moisture supply will be critical, with any shift northwest producing more snowfall across the entire area while a shift toward the southeast will restrict new snow to mainly locations toward the TN-NC border and Great Valley.  The Mountain Empire is on the fence.

*A composite of all models, including Ensembles, plus past climatology of systems embedded within this type of upper air setting suggests that accumulating snow with the main system will reach up to the Virginia-Kentucky border, then taper rapidly toward the northwest and north.  Amounts will increase toward the southeast of the VA-KY stateline, with the High Knob Massif being a local focus via upsloping northerly flow and very cold air to produce low density snowfall. 

Bitter cold is the other main story, with temperatures at just before 5:00 AM Friday varying from 12 degrees atop Eagle Knob of the High Knob Massif to 22 degrees in Clintwood ( a little milder SE toward the Great Valley ).

*Freezing drizzle has been reported into the Great Valley.

Stay tuned for later updates.

Mountain Area Forecast ( January 4-7 )

ALERT For Accumulating Snow & Hazardous Travel Developing Thursday Afternoon Into Friday Morning

Low dewpoint air moving into the Cumbeland Mountains will allow temperatures to drop significantly into Thursday Morning, followed by increasing clouds that keep temperatures cold during Thursday to set the stage for development of a moderate impact snowfall event by late Thursday into Friday.

Widespread hazardous travel conditions are expected to develop during Thursday PM-Evening into Friday Morning.  Bitter temps and wind chills will add to these hazardous conditions.

An ALERT For Accumulating Snow May Be Needed For Late Friday Into Saturday Morning As A Second Wave Impacts The Mountain Region

Overnight Into Thursday Morning

Mostly clear into the overnight then increasing high clouds.  Cold.  W-NW winds 5-15 mph, with higher gusts, becoming light.  Temps in the 10s to low-mid 20s, varying from 10-15 degrees in high valleys of the High Knob Massif to low-mid 20s along exposed middle elevation ridges.

Mid-Morning Thru Thursday Afternoon

Cloudy.  Cold.  Light winds.  Virga developing aloft, then flurries and light snow reaching the surface.  Temperatures generally varying from the 20s to the lower 30s.

Thursday Night Into Friday Morning

Snow.  Turning bitter.  Winds WNW-NNW at 5-15 mph, with higher gusts.  Temperatures dropping into 10s to around 20 degrees ( as cold as 10 degrees at highest elevations ).  Wind chills in the single digits and 10s, except below zero in gusts along upper elevation mountain ridges.  Rime formation in upper elevations.

Friday Afternoon

Morning snow tapering to flurries and snow showers.  Bitter cold.  Winds NW to N at 5-10 mph.  Temps  varying from lower-mid 10s in upper elevations to lower-middle 20s.  Wind chill factors in single digits & 10s ( coldest at highest elevations ).

Snowfall Forecast: Late Thursday to Late Friday

A general 1″ to 4″ of snowfall is expected in counties along the Virginia-Kentucky border, with locally higher amounts possible at upper elevations of the High Knob Massif ( least snowfall amounts are expected across central-western Lee County and portions of the Clinch & Holston river valleys ).

Target Snowfall 3″ In Norton-Wise ( +/- ) 1″ Error Potential.  This suggests a possible range from 2″ to 4″ in Norton-Wise during this period.  Snow Density will be lower than 10:1 in locations along & north to northwest of the High Knob Massif and Tennessee Valley Divide to generate more “fluff factor” than in locations farther to the southeast ( i.e., the snow to water ratio will be locally higher ).

Friday Night Into Saturday Morning

Periods of snow & snow showers.  Heavy at times.  Bitterly cold.  NNW-N winds 5-15 mph, with higher gusts on middle-upper elevation mountain ridges.  Temperatures varying from 0 to 12 degrees.  Wind chills from 5 above to -10 below, except -10 to -20 degrees below zero upper elevation ridges.

A second storm system lifting northeast out of the Gulf of Mexico is now forecast to impact the mountains late Friday into Saturday morning, with an update to the forecast noted above. 

Sunday & Monday morning’s ( January 8-9 ) will both feature bitterly cold temperatures, especially in mountain valleys, with single digits and sub-zero temperatures being possible.  Please stay tuned for later updates.

Weather Discussion ( Harsh Period )

Thursday Afternoon Update

An initial wave of snow dropped 0.5″ to 1″ of accumulation across portions of northern Wise and Dickenson counties into early afternoon Thursday, before waning.

I officially measured 0.5″ of snow in Clintwood, with heavier snow to the north and northeast toward Pine Mountain and Breaks Park.

Although flurries and light snow showers have occurred throughout Wise County, the lower atmosphere south of Pound has not yet been able to saturate with abundant amounts of low-level dry air.

A developing area near Middlesboro on Doppler radar is expected to be the beginning of saturation and sticking snow as it lifts northeast across Lee-Wise counties and northern portions of Scott County into this evening.

This system is coming in waves instead of one consolidated area of energy ( at least at this time ), with an initial wave impacting sites to the north while the current developing area of snow denotes a wave that will impact locations farther to the south ( e.g., Wise County which mostly missed sticking early afternoon snow ).

Conditions for snowfall will be improving into Thursday evening as a low-level wind shift to the NW-N increases upslope into the High Knob Massif area and temperatures begin to turn colder.

Meanwhile, the past several runs of the NAM Model group have become aggressive in spreading the heaviest snow across the Mountain Empire late Friday into Saturday.

The Morristown NWS Forecast Office has issued a Winter Storm Watch for later Friday into Saturday.  I will wait to this initial period passes tonight before updating my snow forecast for this second event.  There remains substantial model disagreement with respect to how much moisture reaches the area.  Stay tuned for later updates.

Previous Discussion

A harsh period of winter conditions will dominate the mountain landscape during upcoming days.  While no big winter storm is expected, the combination of bitter cold air and some snow will create the harsh conditions, especially in a season where this type of weather has been limited.

Rain showers changed to snow showers & flurries into early Wednesday with a little accumulation at high elevations in the High Knob Massif.  The most important aspect; however, was clearing skies with advection of much drier, lower dewpoint air into the mountains.  This will allow for cold conditions into the daylight hours of Thursday, as clouds increase, and set the stage for a Moderate Impact winter event late Thursday into Friday.

A huge mass of bitterly cold air will continue to move south and southeast into the mountains during the next few days. 

The NAM Model group has nearly all the snow falling with the first disturbance across the Cumberland Mountains, as the second and much bigger wave spreads snow across parts of the Deep South into the Carolina’s and the TN-NC border this weekend.  The latest European Model run ( 00z ) has cut back amounts across the board, except for the Deep South & Carolina’s ( a bulls-eye of 12″-15″ being centered mainly on the zone that got devastated by Hurricane Matthew flood waters in central-eastern North Carolina on the ECMWF ).

I always have some Error Potential factored into my snow forecast’s; however, if this reduction trend continues then totals may have to be cut back ( as it stands now, the NAM data would allow it to verify while the new European Run would make it a push to reach the lower end of the range ).

This remains true since models are forecasting at 10:1 density, and with very cold air in the vertical column + a period with moisture intersecting the prime dendritic crystal growth temperature zone the actual snow density will be significantly lower ( snow to water ratios will be higher than 10:1 ).

Regardless of snowfall amounts, conditions are going to be bitter Friday through this weekend with 0 to 10 degrees by Saturday Morning and the potential for even colder MINS, especially in mountain valleys, on Sunday & Monday AM’s.

Update: 1 AM Thursday NAM Model Run

In opposition to the last European Model run, the overnight NAM Model group has come in wetter and also now brings accumulating snow into the mountain area from the next wave tracking across the Deep South.

Clearly, the models are struggling to handle these waves embedded within fast flow aloft tracking across the USA against a huge arctic air mass to the north.

Stay tuned for more updates.

Mountain Area Forecast ( January 2-4 )

A Harsh Period Of Winter Weather Is Becoming Increasingly Likely For The January 5-10 Period

An ALERT For Accumulating Snowfall, Hazardous Travel And Increasingly Bitter Conditions Will Be Likely Issued For The Late Thursday Into Saturday Period ( With Bitter Cold Continuing Into Monday )

*I will issue a new forecast by later Wednesday.

Overnight Into Monday Morning

Cloudy.  Scattered showers.  Areas of drizzle & fog ( dense along upper elevation mountain ridges ).  Mild.  SSE-S winds 5 to 15 mph, with some higher gusts, along mountain ridges below 2700 feet.  Winds S-SW at 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures in the 40s to around 50 degrees.

Monday Afternoon

Cloudy.  Periods of showers.  Thunder possible.  Areas of fog ( dense along upper elevation mountain ridges ).  SSE-SSW winds 5-10 mph, with higher gusts, below 2700 feet.  Winds S-SW at 5-15 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures widespread in the 50s.

Monday Night Into Tuesday Morning

Periods of rain & showers. A chance of thunder.  Local downpours possible.  Areas of fog ( dense fog along upper elevation mountain ridges ).  Winds SSE-S at 5-15 mph, with higher gusts, on ridges & plateaus below 2700 feet.  Winds S-SW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps in the upper 40s to low-mid 50s.

Tuesday Afternoon

A chance of showers, otherwise, partly-mostly cloudy.  Unseasonably mild.  SW winds 10-20 mph, with higher gusts.  Dense fog continuing along high elevation ridges.  Temperatures varying from upper 40s to lower 50s amid upper elevations to upper 50s to low-mid 60s ( warmest in downslope sites around Pound, Clintwood, Haysi, Grundy ).

Tuesday Night Into Mid-Morning Wednesday

Turning colder by morning.  Rain showers changing to snow by morning at mid-upper elevations before ending.  A light accumulation ( dusting ) possible at highest elevations.  SW winds shifting WNW-NW at 10-20 mph, with higher gusts, along middle to upper elevation mountain ridges-plateaus.  Temps dropping into the middle-upper 20s to mid-upper 30s by mid-morning ( coldest at the highest elevations ).  Wind chills dropping into the 10s and 20s.

*Air will turn bitterly cold by Friday into this upcoming weekend.  Snow accumulations look likely for the mountains, but amounts remain in question.  If substantial snow accumulates the potential for air temperatures to drop below zero will increase, especially in mountain valleys.  Sub-zero wind chill factors will be likely across exposed mountain ridges.  Stay tuned for updates as this winter weather episode gets closer.

Weather Discussion ( Mild-Nasty )

Reference My High Country Focus for a brief recap of 2016.  Additional details will be added later to this reveiw section.

A mild and generally nasty period of weather is on tap through early week as abundant low-level moisture will support periods of light rain, drizzle, areas of dense fog, and even some downpours ( with possible thunder ).

This current pattern is not new, as wet and mostly gloomy conditions have dominated the mountain landscape for the past 10 days with generally mild temperatures ( for this time of year, outside of the NW flow snowfall period ).

Some orographic enhancement of rain will be possible by Monday Night Into Tuesday, with heaviest amounts associated with strong to severe thunderstorms over the Deep South.  Time will tell how that may or may not impact rainfall across the Mountain Empire.

While there will be a chance of thunder, due mainly to elevated instability aloft, the risk for severe thunderstorms is currently expected to remain southwest and south of the mountains.

The air mass begins to change & turn colder by  Wednesday into Thursday, with a developing streak of light snow on the NAM Model ( above ) being a subject many are already interested in ( yet it remains too far out in time to know how much snow will fall across the mountains ).

*Note that I outlooked the potential for a HARSH period of winter conditions days ago, not because of any given model but due to the synoptic-scale pattern that is developing.  Bitter air will come and if snow accumulates this will make conditions much colder, that is true, but bitter air will make conditions harsh regardless of snow for at least a few days.

With respect to snowfall potential, past climatology of settings  like this says that two options are most favored:

A ).  The northern stream becomes dominant and forces snow generating energy far to the south, with the only moisture source available being the Great Lakes for upslope snow in locations that can get a fetch from the lakes.

B ).  Cold air arrives but does not dominate initially, with energy in the sub-tropical jet tracking far enough north to generate a band of potentially significant snowfall.  Upslope NW flow snow could then add to amounts along windward slopes in the mountains.

The next couple of days will help determine which scenario will verify, with the MEAN of the 51-Member European Model Group currently going with a snow band development.  It should be noted that if one looks at EACH MEMBER the variation forecast is from less than 1″ up to 6-12″+ .  The MEAN, which often is closer to true reality, is between these extremes.  So it is too soon for anyone to be making an actual forecast of snow amounts.  That will come.

Dual blocks will force cross-polar flow into the USA that will make the DAY 3-7 or DAY 4-8 period ( which ever one you wish to pick out ) very cold, with the local mountains being at the -10 C 850 MB isotherm ( that is a MEAN temp of 14 degrees near the High Knob summit for a 5 day period ).  That will be cold, of course, at all elevations.

So even if snow does not accumulate it will get cold.  If snow cover develops it will become MUCH colder.  Stay tuned for updates on this upcoming wintry period.

*Some moderation is currently being shown by next week, but the pattern is one that looks like it can reload.  So time will tell more as the setting across the eastern Pacific will be very complex.  The Pacific pattern has been forcing our weather, so with limited data points across this expanse it is not surprising that models will be struggling to pin down details of individual systems until they actually reach the North American continent.

Note I say the Pacific has been forcing our pattern, but that Pacific pattern has also been forced by other factors.  A key factor appears to have been a rapid and extensive development of snowpack across Siberia during this past autumn that altered the flow field across the northern Pacific and impacted the Polar Vortex.

Mountain Area Forecast ( Dec 31-Jan 2 )

ALERT For Strong SSW-SW Winds For New Year Eve’s Day ( Saturday ) Is Now In Effect.  ROARING SW Winds Will Develop At Upper Elevations First And Mix Down Into Middle & Lower Elevations Of The Cumberland Mountains During The Day Saturday.

*Following a decrease in winds Friday evening, the gradient tightens again by Saturday morning with another period of ROARING winds ( SW in direction this time ) throughout the daylight hours of New Year Eve’s Day.

A developing temperature inversion late Saturday into Sunday morning, with evaporative cooling, will then restrict strongest winds to highest elevations along top of the planetary boundary layer ( i.e., evaporative cooling will force decoupling as lower levels in the atmosphere cool relative to milder air aloft ).

*The Potential For Snow Or Frozen Precipitation Forms Needs To Be Monitored For New Year Eve’s Afternoon & Evening – Especially In The Southwest Upslope Flow Zone Of Wise, Scott, Lee Counties Along And SW Of The High Knob Massif – Tennessee Valley Divide.

Overnight Into Saturday Morning

Mostly clear.  Cold.  Winds becoming SSW-SW at 10-25 mph, with higher gusts, along middle-upper elevation mountain ridges.  Light valley winds.  Temperatures in the 10s & 20s, varying from single digits to around 10 degrees in sheltered upper elevation valleys to readings rising overnight into morning along mountain ridges ( to low-mid 30s on ridges within the 2000-3000 foot elevation zone ).  Wind chills from single digits & 10s on upper elevation ridges to the teens to lower 20s.

Mid-Morning Through Saturday Afternoon

Increasing clouds with lowering cloud bases over time.  Virga forming aloft with a chance for flurries to light snow developing, especially along and southwest from the High Knob Massif & Tennessee Valley Divide.  Windy & cold.  SSW-SW winds 15-25 mph, with higher gusts, at elevations below 2700 feet.  SW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from upper 20s-low 30s at highest elevations to upper 30s to middle 40s, dropping with the onset of precipitation.  Wind chills in the 10s and 20s.  Dense fog developing at highest elevations.

Saturday Evening Into Sunday Morning

Chance of evening snow ( especially along-southwest of the High Knob Massif-Tennessee Valley Divide ) or mix giving way to rain.  Frozen forms possible in the SW upslope zone.  SSW-WSW winds 10-20 mph, with higher gusts on middle-upper elevation ridges, decreasing into morning.  Temps mainly from the lower 30s to around 40 degrees.  Areas of dense fog.

Sunday Afternoon

Mostly cloudy.  Chance of light showers or drizzle.  Milder.  Winds SSE to SSW at 5-15 mph.  Temperatures in the 40s to around 50 degrees.  Areas of fog, especially at highest elevations along mountain ridges.

Sunday Night Into Monday Morning

Mostly cloudy.  Chance for a light shower or drizzle.  Mild.  Winds SSE-SSW 5-15 mph along mountain ridges-plateaus below 2700 feet.  Winds SSW-SW 10-20 mph, with higher gusts, along upper elevation mountain ridges.  Widespread temperatures in the 40s to around 50 degrees.  Dense fog at highest elevations.

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( More Nasty )

Reference My High Country Focus for a brief recap of 2016.

Saturday Afternoon Update

Flurries and light snow showers have occurred throughout the afternoon of New Year’s Eve Day across the High Knob Massif area of Norton-Wise ( even at low elevations in the downslope zone to Clintwood ).

Conditions have varied from beautiful mountain waves being visible to a reduction in visibility in light snow-flurries ( below ).

The atmosphere has been saturating from the top down, with the summit levels of the High Knob Massif now being obscured in freezing fog ( clouds ) amid flurries-light snow. A small accumulation has recovered roads.  Travel should be avoided on State Route 619, Routes 237, 238, and others in the upper elevations into this evening as frozen precip will continue at times ( fog will become persistent and lower in elevation to below the main crest lines by late evening ).

Winds are simply wicked in upper elevations, with gusts of 40-50+ mph being common.  The 5:15 PM temperature is 29 degrees on Eagle Knob of the High Knob Massif, with 30 at a little lower elevation on adjacent Black Mountain.

Wind have also, of course, been strong in Wise with Lonesome Pine Airport displaying its typical temp bias:

versus adjacent stations at the same elevation:

Surface temperatures from just below to just above freezing will continue into this evening within the upslope flow zone of the High Knob Massif area.

At all locations outside the highest elevations there remains a small temperature-dewpoint depression for evaporative cooling.  Temperatures aloft, above the high summits, should continue to warm to strengthen a low-level temperature inversion.  Strong wind gusts at locations below the elevation of Wise should begin decreasing, while gusty to ROARING winds will continue through the night in upper elevations.  Have a Safe & Happy New Year. 

Previous Discussion

Reference my 123016 Forecast page for details on recent snow.

Reference The High Knob Landform for views of December 2016.

Given wind and chilly conditions with developing virga to surface precipitation through New Year’s Eve and Morning, I have updated my forecast page to clean it up for these next upcoming weather conditions.

Winds are beginning to increase again at upper elevations, and this will continue into Saturday with mixing of higher speeds downward into middle and lower elevations with time ( at least until evaporative cooling begins ).

My main concern for the short-term will be the potential for some snow and frozen precipitation to develop Saturday PM & Saturday Evening, especially in the High Knob Landform corridor where SW air flow rises 1000 to 3000 vertical feet as it streams northeast from Tennessee.  The wind max that is shown above, over the Nation’s Heartland, will be along the Appalachians by New Year Eve Afternoon-Evening.

*Low-level cooling will be greater than models suggest into Saturday Evening, even as temperatures continue to warm aloft, so this threat must be monitored until wind direction’s change.

It is easy to see from this sounding forecast ( above ), that if the surface temperature & dewpoint are just a little closer together at levels downward from the summit of the High Knob Massif ( where orographic lifting occurs ) that the column will be saturated and sub-freezing through a relatively deep layer.  So my concern is a no brainer unless the model is completely out of whack, which is not as likely given current low dewpoint air ( to support cooling ).

Mild air for this time of year will then rule the mountain region from Sunday into Tuesday, with periods of rain, before conditions turn cold once again.

As always, please stay tuned for updates and have a Safe and Happy New Year.

Mountain Area Forecast ( Dec 29-Jan 1 )

ALERT For Snow Showers And Bursts Of Heavy Snow To 10:00 AM Friday.  Snow-Blowing Snow Will Reduce Visibility And Cause Travel To Become Hazardous In Locations Along & West-Northwest Of the High Knob Massif-Tennessee Valley Divide.  Less Snow And Lower Impacts Are Expected Lee Of The Mountains Into The Great Valley ( As Well As Below 1200-1500 Feet ).

A general 1″ to 3″ of snow are likely between Midnight and 10 AM Friday as very cold air aloft moves over the mountains.  This will combine with limited low-level moisture ( a marginal Great Lake event ) and strong WNW-NW winds to develop snow showers and bursts of heavy snow.  Due to very cold air aloft, some bursts may also occur leeward of the mountains in localized portions of the Clinch, Powell, Holston river valleys.

Thursday Night Into Mid-Morning Friday

Cloudy with snow showers & flurries developing.  Bursts of heavy snow.  Colder.  Snow accumulations of 1″-3″ along the upslope side of the mountains, with less than 1″ leeward of the mountains and at elevations below 1200-1500 feet in elevation.  WNW-NW winds 10-25 mph, with higher gusts.  Temps varying from low-mid 10s at the highest elevations to mid-upper 20s.  Wind chills in the single digits and 10s, except below zero ( especially in gusts ) at the highest elevations.  Rime formation in highest elevations.

Mid-Morning Friday Through Friday Afternoon

Snow showers & flurries ending.  Skies becoming partly cloudy.  Cold.  W-WNW winds 10-20 mph, with higher gusts.  Temperatures varying from upper 10s to lower 20s in upper elevations to the upper 20s to lower 30s.  Wind chills in the single digits and 10s, except below zero in stronger gusts at highest elevations.

Friday Night Into Saturday Morning

Mostly clear.  Cold.  Winds becoming SSW-SW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges.  Light valley winds.  Temperatures in the 10s & 20s, varying from single digits to around 10 degrees within upper elevation valleys to readings rising overnight into morning on highest mountain ridges ( to around 32 F ).

Saturday Afternoon

Increasing clouds with lowering cloud bases over time.  Virga forming aloft with a chance for flurries to light snow developing late, especially along and southwest of the High Knob Massif & Tennessee Valley Divide.  Windy & cold.  SSW-SW winds 15-25 mph, with higher gusts, at elevations below 2700 feet.  SW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from around freezing at highest elevations to upper 30s to middle 40s, dropping with onset of precipitation by late.  Wind chills in the 10s and 20s.

Saturday Evening Into Sunday Morning

Chance of evening snow ( especially along-southwest of the High Knob Massif-Tennessee Valley Divide ) or mix giving way to rain.  Freezing rain possible in some valleys.  SSW-WSW winds 10-20 mph, with higher gusts along middle-upper elevation ridges, decreasing into morning.  Temps mainly from low-mid 30s to around 40 degrees.

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( Taste Of Winter )

Friday Snow Report ( December 30, 2016 )

Snow accumulations were widespread across Wise and Dickenson counties into Friday morning.  The most intense period came with a monster snow band that developed along the Virginia-Kentucky border toward 11:00 AM to Midnight, with near zero visibility at its peak and rapid sticking to all objects ( including roads ).

It was a wicked night in the High Knob Massif.  Joe & Darlene Fields measured 1″ of snow depth in High Chaparral by 10:30 to 11:00 PM, before the intense snow band hit.  Wind gusts of 30-40+ mph took wind chills down into single digits above and locally below zero.

Much of the snow in this view ( above ) fell horizontally or even upward in direction ( as you can tell by looking closely at lines made by larger flakes ).  WNW-NW winds of 20 to 40+ mph, of course, caused these conditions along with relatively dry, low water content snow.

Friday Morning Snow Reports

Head of Powell Valley: 1.5″
( 1-2″ AM Depths )

Nora 4 SSE NWS: 1.6″
( 2″ AM Depth )

Clintwood 1 W NWS: 2.0″
( 2″ AM Depth )

UVA-Wise NWS: 2.5″
( 2″ AM Depth )

Norton Water Plant: 2.5″
( 2″ AM Depth )

High Chaparral: 3.0″
( 3″ AM Depth )

Eagle Knob: 3.5″
*( Variable Depths )

*Best estimate of snowfall is 3.0″ to 4.0″ with highly variable   depths from near bare ground to 6″ or more in places.

Previous Discussion

Reference my 122916 Forecast for previous details.

A simply gorgeous sunset Thursday was observed above chilly, gusty conditions in advance of an approaching upper air disturbance featuring very cold air aloft.

Virga and a few flurries-sprinkles falling beneath puffy clouds signals what is upcoming by Midnight to 10 AM Friday as very cold air aloft ( 0 to -30 F below in the 10,000 to 18,000 foot zone ) moves across the mountains to help trigger snow showers, flurries, and some bursts of heavy snow ( squalls ).

Accumulations will primarily be limited to upslope zones with respect to W-NW flow.  The high resolution NAM 4 KM Model has the right idea but is skewed ( as almost always ) with placement and amounts due to terrain recognition problems and a flawed climatology database.

Great Lake connected flow will be marginal at best across the southern Appalachians.  The central Appalachians; however, from central-northern West Virginia northeastward, will be within true Lake moisture for a while as a Nor’easter rapidly intensifies along the New England Coast into Friday ( the negative tilted upper air trough hindering Lake moisture advection farther south into the southern Appalachians in this case ).

Looking ahead, following more wet and mild conditions to open up the New Year in early January, a radical change in the pattern is looking increasingly likely by the January 4-6 period and beyond in time.  High-latitude blocking centers near Greenland and Alaska will force cross-polar flow from snow laden Siberia into North America and the USA.

The potential for a harsh and prolonged period of winter is being monitored as this pattern takes shape, with perhaps a 2-3 week window of particularly bad conditions.  Stay tuned for later updates.

Mountain Area Forecast ( Dec 28-30 )

A Blast Of Cold Air Thursday Into Friday Morning Will Be Enhanced By Strong & Gusty W-NW Winds.  Upslope Snow Showers Are Expected Thursday Night Into Early Friday With Accumulations Varying From A Dusting Up To 3″ ( Mainly Windward Side Of The Mountains ).

Locations along and west to northwest of the High Knob Massif and Tennessee Valley Divide, as well as the TN-NC Border, will be most favored for accumulating snow.

Overnight Into Wednesday Morning

Mostly clear.  Seasonally cold.  Winds WNW-NW at 5-15 mph along mid-upper elevation mountain ridges.  Temperatures varying from 10s in colder mountain valleys to the 20s to lower 30s ( mildest on exposed mountain ridges ).  Areas of mainly river valley and lake fog & freezing fog.

Wednesday Afternoon

Sunny.  Light SSE-S winds mostly less than 10 mph below 2700 feet.  S-SW winds increasing to 5-15 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps varying in the 40s to near 50 degrees.

Wednesday Night Into Thursday Morning

Becoming cloudy & windy.  Rain developing by midnight into the overnight.  A chance of thunder.  Rain ending as snow and/or sleet at highest elevations toward morning.  SSW-W winds 10-20 mph, with higher gusts, at elevations below 2700 feet.  Winds SW to WNW 15-25 mph, with higher gusts, along mountain ridges above 2700 ft.  Evening temps in the low 30s to around 40 degrees, then rising into early overnight before dropping again by morning.

Thursday Afternoon

Partly cloudy & windy.  Turning colder.  W to WNW winds 10-25 mph, with higher gusts.  Temperatures dropping into the mid-upper 20s to the mid-upper 30s ( coldest at highest elevations ).  Wind chills falling into the 10s and 20s, except single digits in gusts at highest elevations by late.

Thursday Night Into Friday Morning

Cloudy with snow showers & flurries developing.  Colder.  Snow accumulations of 1″-3″ along the upslope side of the mountains, with less than 1″ leeward of the mountains and at elevations below 1500 feet in elevation.  WNW-NW winds 10-25 mph, with higher gusts.  Temps varying from low-mid 10s at the highest elevations to mid-upper 20s.  Wind chills in the single digits and 10s, except below zero ( especially in gusts ) at the highest elevations.

*Another heavy precipitation event is now being watched for this weekend into early next week.  Precipitation may begin as snow or a mixture on Saturday ( December 31 ) before changing to all rain in all locations.  Heavy rain and strong rises on streams & rivers could occur early next week.  Stay tuned for later updates.   

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( Big Changes )

Wednesday Evening Update

Evening temperature have fallen rapidly to around 30-35 degrees in mountain valleys, ahead of thickening clouds with a band of rain and some embedded thunder.  I have updated the forecast to account for this steep evening temperature drop and to add a chance of thunder with elevated instability above a cold boundary layer.

This will be adding more water to creeks that are already gushing with water pouring out of the High Knob Massif.

Temperatures should rise in valleys as strong and gusty winds mix throughout the vertical depth of the atmosphere with wind driven rains arriving in a couple more hours.

Previous Discussion

Much like the virtual switch flip from dryness to wetness that occurred in late November through December, another flip of the weather switch will occur in early January to kick off what I think will be a prolonged, harsh period of winter.

Meanwhile, rapid fire weather changes will continue into this weekend and early next week as a very active pattern continues to impact the mountain region.

The rise and drop of water levels on steep creeks draining the High Knob Massif during this past month tells the tale of wetness, with 7.00″ to 11.00″+ now having fallen just in December ( several inches more if adding late November ).

A total of 10.33″ were measured in the City of Norton, at base of the High Knob Massif, from November 28 to 9:00 AM December 27  ( with moderate-heavy rain falling at observation time Dec 27 ).

*Around 15.00″ or more of total precipitation has fallen across the head of Big Cherry Lake basin during the 1-month period between November 28 and December 27.  This NOT including substantial secondary moisture from RIME deposition on trees and fog drip from trees added to the watershed during this period.

A total water level rise of 12.5 vertical FEET has occurred on Big Cherry Lake in the High Knob Massif, with a significant overflow of its spillway causing a ROAR of whitewater on South Fork of the Powell River through South Fork Gorge.

Observe the dewpoint drop as dry air advection occurs into upper elevations ( from 2:45 AM to 4:35 AM ).  This dry air will enhance cold air drainage into deep valleys that decouple from boundary layer winds, especially in upper elevations, with mixing of this drier air into lower elevations after sunrise Wednesday.

Although winds remain brisk on high mountain ridges, the valleys are going calm and temperatures are really starting to drop as dewpoints are falling through the 10s at highest elevations to supply drier air for drainage into valleys.

A similar 900-800 MB dry air supported drop occurred in high valleys of the High Knob Massif on December 19-20.

The MIN in Wise reached 18 degrees, at the University Of Virginia’s official NWS Station, with 19 degrees at the official NWS station in Clintwood ( the Big Cherry Wetland Valley sensor being calibrated and checked by National Weather Service equipment in Clintwood prior to placement ).

A similar setting was observed during December 19-20 when the MIN temperature fell to 10 degrees in the Big Cherry Lake Wetland Valleys.  Although this was 6 degrees colder than in Burkes Garden and 11 degrees colder than recorded in Shady Valley, it illustrates the range that often occurs in our mountains that is never fully recognized.  The Big Cherry Wetland Valley sensor site likely not being in the coldest spot within high valleys of the massif.

While high mountain valleys in the Cumberland Mountains, especially those in the High Knob Massif, will tend to be the coldest by Wednesday morning, valleys in many locations will experience significant drops during the predawn to post-sunrise period ( especially where fog does not form ).

Sunny skies and dry air will promote a rapid temp rise in valleys Wednesday ahead of the next rapid fire weather change featuring another round of rain that gives way to arctic air and snow showers by Thursday Night.

Bombogenesis of low pressure along the New England coast will wrap most abundant moisture into windward slopes of the Appalachians from central-northern West Virginia northeastward, with 6-10″+ accumulating within  elevations above 3000 feet.

Meanwhile, the Mountain Empire only has a grazing shot with 1-3″ generally expected along windward slopes in the favored locations ( the model, as typical, not picking up on the High Knob Massif-Black Mountain area and its adjacent upslope snowbelt zone ).  Only flurries are likely leeward of the mountains, in much of the Tennessee Valley, with less than 1″ in general at elevations below 1500 feet in all sites.

This marks only the beginning of major weather changes upcoming as December passes into January.  You will want to stay tuned to MANY changes ahead.

Mountain Area Forecast ( Dec 26-28 )

Dense Fog Will Continue To Impact Portions Of The Area Into Monday Morning.  Fog Will Be Most Dense And Widespread In Valleys At Lower Elevations As Well As Along Upper Elevation Mountain Ridges.

Strong & Gusty S-SW Winds Will Impact The Mountain Area Monday Into Tuesday Morning ( Gusts of 30-40+ MPH ).  Mid-Upper Elevations Will Generally Have The Strongest Winds Outside Of Local Mountain Waves That May Reach Valley Floors In Favored Zones. 

A Squall Line Of Rain, With Embedded Thunderstorms, Will Be Possible By Tuesday Morning With Downpours Of Heavy Rainfall.

Overnight Into Monday Morning

Areas of dense fog ( especially in valleys at lower elevations and on upper elevation mountain ridges ).  SSE-SSW winds at 5-15 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet.  S to SSW winds 15-25 mph, with higher gusts, along mountain ridges above 2700 feet.  Mild with temperatures in the 40s to low-mid 50s ( upper 30s to lower 40s in coolest mountain valleys ).

Monday Afternoon

Partly cloudy.  Unseasonably mild.  Windy.  SSE-SSW winds 10-20 mph, with higher gusts, below 2700 feet.  SSW to SW winds 15 to 25 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures varying from low-mid 50s in upper elevations to the low-mid 60s.

Monday Night Into Tuesday Morning

Showers with a chance for thunderstorms.  Locally heavy rainfall.  Windy.  SSW-SW winds 15-25 mph, with higher gusts on mountain ridges-plateaus below 2700 feet.  SW to WSW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Unseasonably mild.  Temperatures widespread in the 50s to near 60 degrees.

Tuesday Afternoon

Skies becoming partly to mostly sunny.  Turning cooler.  Winds shifting W at 5-15 mph with higher gusts.  Temps dropping into the 40s by late, except into 30s at highest elevations.  Wind chills dropping into the 20s and 30s by late afternoon ( coldest at highest elevations ).

Tuesday Night Into Wednesday Morning

Mostly clear.  Seasonally cold.  Winds WNW-NW at 5-10 mph along mid-upper elevation mountain ridges.  Temperatures varying from 10s in colder mountain valleys to the 20s to lower 30s ( mildest on exposed mountain ridges ).

Much colder air will arrive Thursday into Friday with a chance for snow showers and flurries.  Some accumulations will be possible.  Stay tuned for updates on this wintry weather.

Weather Discussion ( Changeable )

Late Monday Evening Update

Strong and gusty SSW-SW winds are blowing across the area tonight in advance of an approaching cold front and line of showers with embedded thunderstorms.

Frequent wind gusts around 40 mph are being recorded along high mountain ridges, with 25 to 35 mph gusts common across middle elevation ridges & plateaus.  Locally strong wind gusts will occur in some valleys northeast of the high terrain.  Dense fog, with cap clouds, continues to obscure high mountain ridges along & to the southwest of the High Knob Massif and Tennessee Valley Divide.

Current inflow and wind streamlines are near the long-term mean climatology; although, models like the GFS do not recognize this and are forecasting little rainfall.

High resolution models that have better resolution are picking up on a downpour potential that will occur as the boundary nears during the predawn-morning period.

Very dry air advects ( is transported ) into the area later Tuesday, with clearing skies that sets the stage for frosty cold conditions into Wednesday morning when I expect a large vertical temperature spread between 10s in colder valleys and 20s to lower 30s ( mildest on exposed ridges ).

*High valleys in the High Knob Massif will fall to around 10 degrees if boundary layer winds can decouple, with strong drainage of cold air into the basins.

Previous Discussion

The History Of Christmases Past will be adding in 2016 with headlines for wet & foggy conditions, as abundant low-level moisture ruled the mountain landscape during the holiday.

Another significant rain event accompanied the foggy conditions with a widespread 1.00″ to 1.50″ being observed in counties along the Virginia-Kentucky border in the Cumberland Mountains.

December 2016 precipitation totals of 5.00″ to 10.00″ have been observed, with yet more coming to close out the month and year.

*Max precipitation totals occurring in the High Knob Massif where steep creeks have been gushing and mountain lakes overflowing with run-off.

While valleys have areas of dense fog, with light to calm winds, higher mountain ridges are engulfed in low clouds amid strong & gusty S-SSW winds.  Locations in between will experience the best visibility into early Monday.

Strong upsloping SSW-WSW winds will work to lower cloud bases again into Monday Night and Tuesday Morning as rain showers and a line of rain, with possible embedded thunder, develops across the mountain area.

The lower atmosphere is very moist and the air mass will be unseasonably mild for this time of year as the next wind driven front arrives by the predawn-morning hours of Tuesday.

A very photogenic storm system is sprawling across the USA at the current time, with a developing line of rain and thunderstorms.  The downpour potential with this should not be under-estimated as it arrives overnight into Tuesday morning, especially within favored SW upslope flow zones of the High Knob Landform and TN Valley Divide corridor.

A changing pattern is upcoming by late this week into the first week of January 2017 as blocking develops at higher latitudes in the vicinity of Greenland and Alaska, forcing negative dips in both the North Atlantic & Eastern Pacific oscillations = colder conditions with increased chances for wintry precipitation ( around or after the Jan 4-6 period ).

Stay tuned for updates on this changing pattern.

Mountain Area Forecast ( Dec 22-25 )

An ALERT For Strong S-SW Winds From Late Friday Into Christmas Eve Morning.  Wind Gusts of 30-50+ MPH Will Be Possible, Especially At Middle-Upper Elevations And With Any Mountain Waves.

The Potential For Heavy Rainfall, With Embedded Thunder Possible, Will Develop Into Christmas Eve Morning.  Abundant Low-Level Moisture Will Linger Behind The Heavier Rain Shield Into Christmas.

Overnight Into Thursday Morning

Partly-mostly cloudy.  Windy.  SW-WSW winds 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges & plateaus.  Temps varying from 30s in the sheltered valleys to the 40s across exposed locations, then dropping into 30s toward morning in upper elevations ( to around freezing on highest peaks ).  Wind chills in the 30s and 20s, except 10s in gusts on high peaks toward morning.

Thursday Afternoon

Partly cloudy ( increasing clouds late ).  Winds shifting NW-N at 5-15 mph, with higher gusts.  Temperatures varying from low-mid 30s in upper elevations to the low-mid 40s, tending to drop during mid-late afternoon.  Wind chills in the 20s & 30s, except 10s at highest elevations.

Thursday Night Into Friday Morning

Mostly cloudy ( mid-high clouds ).  Northerly winds shifting E-SSE at 5-10 mph on mid-upper elevation mountain ridges.  Temperatures varying from upper 10s to lower 20s in the colder valleys to the upper 20s to lower 30s ( rising toward morning into the mid-upper 30s on high mountain ridges ).

Friday Afternoon

Mostly cloudy.  Windy.  SSE-SSW winds 10-20 mph, with higher gusts, especially across mid-upper elevation ridges and plateaus.  Temperatures mainly in the 40s to lower 50s.

Friday Night Into Christmas Eve Morning

Cloudy & windy.  Rain developing, with a chance for thunder, overnight into morning.  Locally heavy rainfall.  Winds SSE-SSW at 10-20 mph, with higher gusts, below 2700 feet.  Winds SSW-SW 20-35 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from upper 30s to mid-upper 40s.  Areas of fog.

Areas of fog will be across the mountain area Christmas Eve Day into Christmas Morning.  Widespread, dense fog will be likely at upper elevations in orographic clouds ( capping pilatus ).  Dense fog could also develop at other locations.  Remain alert for these conditions as abundant low-level moisture engulfs the area.

Christmas Eve Afternoon

Cloudy.  Heavy rain & possible thunder giving way to showers.  Areas of fog.  Gusty SW winds decreasing to 5-15 mph, with higher gusts, along mountain ridges below 2700 feet.  Winds SW-W at 10-20 mph on mountain ridges above 2700 feet.  Temperatures in the 40s to around 50 degrees.

Christmas Eve Into Christmas Morning

Cloudy ( abundant low-level moisture ).  A chance of showers-drizzle and areas of dense fog.  SW-W winds 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges.  Seasonally mild with temps in the 40s to lower 50s.

Weather Discussion ( Wet Holiday )

Thursday Night Update

I have updated my forecast into the Christmas Holiday to increase wind speeds for late Friday into Saturday morning, with another strong low-level jet set to ROAR.

This also sets the stage for another rainfall enhancement episode with strong orographic forcing in the High Knob Massif-Black Mountain corridor.  Rain amounts of 1.00″ to 1.50″+ are looking likely in this area, to include the City of Norton ( within the massif’s lifting zone on SW air flow ).

Again it must be stressed that abundant low-level moisture lingers after the heavier rains pass, such that fog, drizzle and a few showers are likely to remain factors into at least mid-morning on Christmas day.

The Wettest Area In Virginia – Climate Notes

The pattern of low-level inflow into the mountain area has recently ( above ) been very close to long-term annual mean flow at the surface ( below ).

The long-term 925 MB flow ( below ), which is often near the elevation of Wise, has also been nearly identical to surface flow observed during this wet pattern.

 The current pattern reveals one factor ( of which there are many ) that makes the High Knob Massif area the wettest in Virginia, with a MEAN SW flow observed in the surface-925 MB layer ( the lowest portion of the atmosphere which is orographically lifted into the middle-upper elevations ).

In looking at air flow trajectories for any given location, it is very important in the Appalachians ( or any mountains ) to observe what lies UPstream.  In this case, a short and/or long-term SW flow can stream into the High Knob Massif area from the Gulf of Mexico without having to first cross high mountains upstream ( between the Gulf and massif ).  Much of the flow can actually stream up the open expanse of the Tennessee Valley to reach the High Knob Massif.

On the other hand, by dramatic contrast, a short and/or long-term SW flow reaching Mount Rogers-Whitetop must cross MANY high mountains upstream ( between the Gulf and Mount Rogers-Whitetop ).  In this case many repeated up-down slope motions have occurred to extract moisture from the air mass by the time it reaches what has always been assumed to be the wettest area in Virginia ( * ).

*Since Mount Rogers & Whitetop Mountain are the two highest in Virginia, most everyone assumed they were also the wettest given their higher elevations.  However, as has also been noted by other researchers ( such as Baker Perry and Charles Konrad ) elevation is only a single factor of MANY that collectively dictate the precip regime of any given area within the southern Appalachians.

The following are RAW data files containing precipitation observed by the AFWS ( IFLOWS ) System since September 30 ( at 7 AM ) for both Eagle Knob of the High Knob Massif and Whitetop Mountain.  The bulk of this falling since late November 2016.

Eagle Knob of High Knob Massif IFLOWS Since 093016

It should be noted that BOTH rain gauges have undercatches due to strong winds, with estimated values being on the order of 20-30% given direct comparison of such gauges to hand-measured NWS rain gauges ( i.e., we do a direct comparison between the IFLOWS at Big Cherry Dam and a NWS rain gauge, and during many past years I have compared the Eagle Knob IFLOWS to both NWS and other rain gauges ).  In other words, both of these gauges have likely caught only 70-80% of what has actually fallen ( these undercatches increase greatly for snow, but snowfall has been very limited to make this an excellent period for comparisons ).

Whitetop Mountain IFLOWS Since 093016

Even if the Whitetop Mountain undercatch is 30% versus 20% on Eagle Knob the difference holds ( actually increases a little ) between the two sites.  This is not a fluke, as per my observations during the past few decades this is intimately connected to air flow trajectories shown above and the up-stream air flow differences between each site and the Gulf of Mexico moisture source.

**Note I have never directly compared the Whitetop Mountain IFLOWS to a NWS rain gauge.  However, on Eagle Knob, I have measured differences of up to 60% or more on undercatches in rainfall during extreme wind events.  The IFLOWS loss on heavy and/or prolonged winter storm events can often be greater and more extreme than the most extreme wind driven rain events.

Apart from just looking at two wind swept peaks, I have complete confidence that the High Knob Massif area is the wettest in Virginia given many rain gauge records from a variety of elevations and exposures over long-time periods versus a similar set of sites in the Mount Rogers-Whitetop area of southwestern Virginia.

Previous Discussion & History Of Past Christmases

Rain and abundant low-level moisture will make the Christmas Eve to Christmas Morning period WET, NOT  white in 2016.

History Of Christmases Past ( 1963-2015 )

For lovers of snow, and memories passed, I have included a local history of Christmases dating back to 1963 when only Clintwood and Wise data was available.  I began adding in more information during the 1980s and 1990s when I started my climate research in the High Knob Massif area.

The above rime forming in the traditional manner via orographic forcing with upsloping across mid-upper elevations into December 19.  Freezing fog on December 20-21; however, formed via radiational cooling and near calm conditions at lower-middle elevations with an apparent combination of hoar frost and rime.  Hoar frost being by strict definition a deposition from gas to solid, while rime represents deposition from liquid to solid.  Supercooled vapor was present in both cases ( water can exist in a liquid state in clean air down to temperatures of -40 Celsius, or even lower in certain conditions, before it spontaneously begins to freeze ).

*A lingering inversion, the same basic one that said we would get very little snowfall with more mix and fog initially, has been responsible for this shift into lower elevations as drier air aloft mixed downward across higher elevations.

Abundant surface deposition in local parts of the Great Valley indicated an abundance of nucleation centers for crystal growth, likely from impurities in the air.  This may have supported both hoar frost and non-dynamic rime formation ( since rime formation is typically a dynamic process occurring with cold air advection and wind as air is physically forced to rise by the terrain in higher, mountainous locations of the Appalachians ).  Around 10 rime formation days have occurred in the High Knob Massif this month, with rime deposition on trees & vegetation being part of an important secondary moisture source ( along with fog drip from trees ) that adds substantially to the annual moisture budgets of locations like the lofty basins of Big Cherry Lake and High Knob Lake.

Some 18 of the past 28 years have featured snow cover in upper elevations of the great High Knob Massif, with the High Knob Lake basin being the area that I have used for general record keeping.  A white Christmas being one with at least 0.5″ of snow depth ( since we officially round snow depth to the nearest EVEN whole inch ).

As my brief history of the past reveals, there have been many wet Christmas Holiday periods since 1963.  This year adds another to the record, like in 2015, to keep whitewater rolling on steep creeks draining the High Knob Massif.

While models are not yet set on the exact axis of heaviest rainfall, it is clear that another moderate-heavy round of rain is set to develop across the Tennessee Valley into parts of the western Appalachian front range ( with past climo on this type of flow field supporting this basic solution ).

An abundance of low-level moisture is likely to engulf the area and linger again, partially being trapped beneath yet another low-level inversion.  So caution is advised for those traveling during the Holiday period.  After an autumn were rainfall was difficult to find, now moisture is becoming a nemesis as December has become very wet.  Yet a snow drought continues for now.  Could that end be in sight?  

Check back later for updates on what may be the end to our snow drought ( at least in the mountains ).

MAY YOUR HOLIDAY BE SAFE AND BLESSED.