ALERT For A Heavy To Crippling Fall Of Snow During Sunday ( December 9 )
Snowfall rates during the predawn to mid-day period of Sunday are currently targeted to be most extreme, with many roads likely becoming impassible. Travel should be avoided and plans to be where you expect to stay Sunday should be made now.
Excessive Snowfall Alert For Mid-Upper Elevations of the High Knob Massif And Tennessee Valley Divide
This now includes the Norton-Wise Area
Prepare for impassible roads and the potential of power outages developing Sunday, especially in locations along and southeast of the VA-KY line, where snow depths of a foot or more will be likely.
ALERT For Blizzard Conditions At Upper Elevations In The High Knob Massif
Strong ESE-ENE winds, with gusts over 40 mph, will generate blizzard conditions and make all roadways impassible at upper elevations.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Forecast Model Discussion
The upcoming storm event will generate huge snowfall gradients, both regionally on the synoptic-scale ( or large scale ) and locally on the meso-scale ( or short distances ).
A general southward shift has been observed in the GFS and European models during the past 24-hours; however, not all ensemble members are so aggressive with pushing it south. This southward shift is due to stronger High pressure to the north acting to suppress this classic snow storm track.
*The new GFS-FV3 has remained more consistent and farther north with the storm and heavy snow versus the operational GFS model ( as has the GEM noted below and the JMA continues to bring 10-12″ into the Wise area ).
Most forecasting mistakes are made by jumping onto such radical changes, instead of forecasting for the pattern and using past climatology as the reference with past analog storm events (well documented settings).
How models are struggling can be illustrated just today by differences between the 7 AM run of the NAM Model and its latest 1 PM run.
NAM 12 KM Model Run At 7:00 AM Friday
NAM 12 KM Model Run At 1:00 PM Friday
Observe how snowfall at the Wise gridpoint varied from 2″ on the 7:00 AM run to 17″ on the 1:00 PM run (thus the problem at hand).
NAM 12 KM Model Run At 1:00 PM Friday – December 7, 2018
Of global-scale models the Canadian remains firm with a heavy hit, but this operational form can not resolve terrain features very well ( that requires the RGEM 48-hour model ).
Canadian (GEM) Model Run At 7:00 AM Friday – December 7, 2018
The 12z European Model group (7AM Friday run) varied from less than 2″ to more than 12″ at the Wise gridpoint, with 5-6″ being the ensemble mean. It is important to remember that snowfall in Wise tends to be underestimated by this model under the best of circumstances.
Saturday Afternoon Update ( Below )
Mesoscale Snow Depth Forecast
My forecast reflects excessive snow amounts, with a general 1 to 2 feet of snow expected from the Norton-Wise area upward into the high country of the High Knob Massif. This will also include areas along the Tennessee Valley Divide ( higher ridges-plateaus from Sandy Ridge and Hazel Mountain to Big A Mountain and the Black Mountains ).
Blowing & drifting snow will complicate this setting at upper elevations in the High Knob Massif where depths may top 2 feet.
Snow amounts of 6-12″, with locally higher amounts, are expected at elevations below 2000 feet m.s.l. to the north toward Pound and Clintwood.
Snow amounts within the Powell River Valley and the Powell Valley corridor remain most problematic and will be largely dependent upon the development, or not, of a rain-snow transition zone. If this develops amounts in this corridor will remain lower versus if precipitation remains all snow.
At this time my forecast is based upon downsloping on easterly air flow across the High Knob high country being supportive of a rain-mix transition zone developing over Powell Valley, with a TIM Circulation forming in which cold air will be forced to orographically rise while warming with terrain enhanced subsidence will occur over Powell Valley.
Doppler radar bright-banding, with a notable linear edge against the high country side, will develop if this occurs.
Rain, snow, sleet will all be possible in the transition zone.
Updated Storm Snowfall Forecast – Made December 8, 2018
By the way, these are the Appa-LATCH-ians not the Appa-LAY-ians as many say ( a disrespectful way to speak about these mountains in the view of many long-time residents and pioneer descendants ).
Based on weak-moderate TIM Circulation development, exclusively identified by Wayne Browning, I expect that a large gradient in snow depths to develop across southern and central portions of Wise County and northern portions of Scott-Lee counties (differences highlighted above are not as great as observed during the January 1998 and December 2009 storm events given this storm is not expected to be as strong as those systems).
850 MB Moisture and Streamline Forecast At 7:00 AM Sunday 925 MB Moisture and Streamline Forecast At 7:00 AM Sunday
It is nearly impossible for the floor of Powell Valley, southwest of the Valley Head, to accumulate significant snow on easterly (E-SE) flow streaming across the high country of the High Knob Massif. So, if this type of flow develops I expect most of the accumulation toward Big Stone Gap to occur after low-level flow shifts more northerly in direction late Sunday.
Meanwhile, the 7 PM Friday NAM Model group is in and predicts 10″ to 13″ for the Wise gridpoint.
NAM 12 KM Model Run At 7:00 PM Friday – December 7, 2018
The 12 KM NAM should not be used for mesoscale forecasting, but it can be used for other purposes with the NAM group often being good in complex terrain once weaknesses are learned for any given location and compensated for by forecasters.
Here I am talking about highly detailed local forecasting amid complex terrain (above), as it is obvious by looking at this graphic the model is not accounting for local terrain variations.
A problem with the 3 KM NAM (below) by contrast, is that it tends to over-predict snow in orographic locations near the eastern Continental Divide and to under-predict snowfall in favored lifting zones (like the High Knob Massif) removed from this divide.
Increase the resolution to 3 KM; however, the model becomes much better ( below ). Note it is predicting more than a foot of snow over Big Cherry Lake basin and the High Knob Massif and as little as 2″ in Powell Valley. Although this will NOT capture the true, real life gradient it has the right idea versus the broad-brushed depiction shown by the 12 KM NAM.
NAM 3 KM Model Run At 7:00 PM Friday – December 7, 2018
The latest GFS-FV3 is supporting heavy-excessive snowfall with its 7:00 PM Friday run.
GFS-FV3 Model Run 7:00 PM Friday – Total 66h Precipitation
The latest GEM (Canadian) model run continues to predict heavy-excessive snowfall.
GEM Model Run At 7:00 PM Friday – December 7, 2018
Model Runs And Saturday Thoughts
Model runs Saturday have all come in stronger with the storm system, illustrating that the Friday wobble was just that and the pattern is what must always be forecast. Past such events have hammered the local mountains and there is no current indications to say this will not again happen; although, hopefully not to the extent of January 1998 and December 2009.
NAM 12 KM Model Run At 7 AM Saturday – December 8, 2018NAM 12 KM Model Run At 1:00 PM Saturday – December 8, 2018NAM 3 KM Model Run At 7:00 AM Saturday – December 8, 2018NAM 3 KM Model Run At 1:00 PM Saturday – December 8, 2018Canadian GEM Model Run At 7:00 AM Saturday – December 8, 2018GFS-FV3 Model Run At 7:00 AM Saturday – Total Precipitation
The GFS-FV3 is in test mode, being developed to replace the operational GFS package which has major problems related to its mathematical-physical parameterizations of many processes within its atmospheric boundaries.
GFS-FV3 Model Run At 1:00 PM Saturday – Total Precipitation
The 7:00 AM run of the European Model increased its prediction to 14″ for the Wise gridpoint, in line with the NAM Model; although, some ensemble members were higher and some lower ( the 51-member mean was 11″ and well above their Friday forecast ).
NAM 12 KM Model Run At 7:00 PM Saturday – December 8, 2018
The 7:00 PM Saturday NAM Model run is nearly identical to its 1:00 PM forecast, with 16″ to 22″ predicted at the Wise gridpoint.
NAM 3 KM Model Run At 7:00 PM Saturday – December 8, 2018
Caution Is Advised For Slick Patches On Roadways, Especially Secondary Routes, into Thursday Morning
Former Alerts
Expect Widespread Sticking Snow Along and West to North of the High Knob Massif and Tennessee Valley Divide Into Wednesday AM
ALERT For Accumulating Snowfall Monday Night Into Tuesday Morning and during Tuesday Night Into Mid-Morning Wednesday
Great Lake connected NW Flow snow showers & flurries will develop by Monday night into Tuesday morning along and NW-N of the High Knob Massif-Tennessee Valley Divide.
Showers of sleet, locally heavy, have also been added to the forecast ( especially at low-middle elevations Monday night ).
Slippery road conditions will be possible during these time periods, especially on secondary roads. Low cloud bases are expected to produce a prolonged period of rime formation at upper elevations in the High Knob Massif ( on trees ).
An upper air disturbance and NW-WNW flow will cause snow during Tuesday night into mid-morning Wednesday with somewhat deeper moisture and colder air aloft. Due to cold air aloft, local snow squalls (snow bursts) will remain possible into the afternoon.
**NOTE: Travelers should use caution at highest elevations in the High Knob Massif along Routes 237, 238, State Route 619 and other Forest Service roads due to lingering limbs and cut trees along roadways in wake of the major ice storm of November 15 as documented and forecast at 111118 Forecast.
Overnight Into Monday Morning
Mostly clear and windy, then becoming partly to mostly cloudy. Winds SW-W at 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges & exposed plateaus. Temperatures widespread in the 40s to lower 50s. Wind chills in the 30s & 40s ( coolest upper elevations ).
Monday Afternoon
Becoming cloudy & turning colder. Lowering cloud bases by late. Winds shifting WNW-NW at 5-15 mph with higher gusts. Temperatures falling through the 40s at low-mid elevations and through the 30s upper elevations ( to around freezing highest elevations ).
Monday Night Into Mid-Morning Tuesday
Snow showers and flurries developing, with showers of sleet during the evening (especially at lower-mid elevations). Winds NW at 5-15 mph with higher gusts. Temperatures dropping into the lower 30s to the lower 20s ( coldest at highest elevations ). Wind chill factors in the 10s & 20s, except single digits in gusts highest peaks. Riming on trees at upper elevations.
Tuesday Afternoon
Mostly cloudy & cold. Chance of flurries and snow showers. NW winds 5-10 mph with some higher gusts. Temperatures varying from 20s in upper elevations to the low-mid 30s at low-mid elevations along & NW-N of the High Knob Massif-Tennessee Valley Divide. Wind chills in the 10s & 20s. Riming on trees at highest elevations.
Tuesday Night Into Mid-Morning Wednesday
Light snow, snow showers & flurries. Bursts of locally heavy snowfall. Winds NNW-WNW at 5-10 mph, with higher gusts. Temperatures varying from mid-upper 10s to the upper 20s ( coldest at highest elevations ). Wind chills in single digits & 10s to lower 20s ( coldest highest elevations ). Riming at upper elevations.
Wednesday Afternoon
Snow showers & flurries. Bursts of locally heavy snow possible, especially during early-mid afternoon. WNW to NW winds 5-15 mph with higher gusts. Temps in the 10s to lower 20s upper elevations to the 20s to around 30 degrees low-mid elevations. Wind chills in the 10s and single digits (coldest high elevations).
Updated Forecast:
*Snowfall Forecast Monday Night Into Wednesday
General 1″ to 3″ with locally higher amounts for locations along and north-west of the High Knob Massif and Tennessee Valley Divide.
No sticking up to locally 1″ in downslope locations.
*Another period of accumulating snow is expected during Thursday night into Friday morning.
*The potential for major winter storm development is being monitored for the December 9-11 period. Odds are now increasing for a crippling snow event in the southern Appalachians. Stay tuned for later updates on timing, amounts, and placement of heaviest snow.
Weather Discussion ( Short-Term )
Widespread light snow accumulations, at elevations above 2000 feet, were observed into morning hours of Tuesday within locations along and west-north of the High Knob Massif and Tennessee Valley Divide on NW upslope flow.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A upper air wave and pocket of cold air aloft will combine with a continuation of NW-W flow to caused widespread snow accumulations at all elevations along and north to west of the High Knob Massif & Tennessee Valley Divide during Tuesday night into Wednesday.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Wednesday was a wintry day across the mountain area with widespread 1″ to 4″+ snow accumulations during this event ( 4″ in Clintwood and 2″ to 4″+ snow depths across the Wise-Norton and High Knob Massif area ).
Crippling Snowfall Potential
Looking ahead a crippling snowfall potential is being monitored for the December 9-10 period, but specific details will have to wait until this system comes into view of short-range terrain models.
GFS 21-Member Ensemble Mean Total Snowfall Forecast
The current ensemble mean for the 21-members of the GFS Model is similar to the 51-member mean of what is often the superior European Model (although, the GFS tends to better define the High Knob Massif ).
*I am not allowed to show the European Model information without a very expensive license to legally display its more detailed forecast graphics.
The Wednesday range of the 51-Ensemble Members of the European Model had predicted snowfall totals for the December 8-10 event varying from less than 2″ to more than 24″ at the Wise gridpoint, but the MEAN between all ensembles and the operational run was firmly within the 12″ to 18″ range.
There is likely to be a huge snow depth variation across the area, with not only snow amounts but the density of snowfall being critical factors to impacts.
Locations severely impacted by the January 1998 and December 2009 storm events initially look to be at the greatest risk once again from this storm. Stay tuned for later updates as details become defined.
ALERT For Strong Southerly Winds Saturday Afternoon & Evening With 20-40+ MPH Gusts (Especially At Mid-Upper Elevations)
Residents and travelers at mid-upper elevations should use caution and be alert for the possibility of breaking-falling tree limbs, etc…given wet soil conditions and strong gusts.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Strong winds are generating an array of orographic cloud forms across the High Knob Massif area, with both standing waves and other types ( like lenticular ) being observed.
Black Mountain Mesonet
I first highlighted the possible need for an alert in my headlines for the 113018 Forecast period.
Lonesome Pine Airport In Wise
*A wintry pattern returns next week with cold air and several possible snow and rime producing waves.
The first period of interest for snow and cold being during December 4-7, with orographic upslope flow enhancement on NW-N flow. Rime formation is now expected to begin in the High Knob Massif, at upper elevations, by later on Monday ( December 3 ).
*The potential for major winter storm development is being monitored for the December 8-9 period. A more widespread regional impact exists during this time.
ALERT For Dense Fog At Mid-Upper Elevations Along And SW of the High Knob Massif-Tennessee Valley Divide ( This Includes The Town of Wise )
High Knob Massif Webcam – University Of Virginia’s College At Wise
Now that the low-level jet streak has passed ( which was only predicted here ) the ALERT is now changed to one for low clouds bases ( Dense Fog ) with SW upslope flow.
Lonesome Pine Airport
Travelers should use extreme caution along U.S. 23 through the head of Powell Valley where this type of flow can often generate some of the most dense fog.
Former Alert
ALERT For A Period Of Strong SSW to WSW Winds Developing Into Friday Morning — Especially At The Middle-Upper Elevations
A low-level jet streak near the 850 MB level will move over the mountains into Friday morning. Wind gusts of 20-40+ mph will develop at mid-upper elevations, with local gusts over 50 mph being possible on the highest peaks.
*Rain showers will continue overnight into morning hours of Friday, becoming increasingly wind driven and locally heavy. Downpours will be most likely with strong SW upslope flow into the High Knob Massif and Tennessee Valley Divide.
Expect the high country to be engulfed in clouds, with fog drip from trees adding to rainfall, throughout Friday into Saturday morning across the High Knob Massif.
*A wet pattern will continue into early Sunday with another round of strong winds. Another ALERT may be needed on Saturday.
Another prolonged period in the clouds, with fog drip from trees, will develop later Saturday into Sunday at the upper elevations in the High Knob Massif.
*A wintry pattern develops next week. Systems with possible accumulating snow are being monitored for the December 4-6 and December 8-9 periods. Stay tuned for later timing updates.
ALERT Continues For Hazardous Conditions Into Wednesday Morning With Unseasonable Cold and Slick Roads ( Patchy snow on main roads, widespread snow on secondary roads )
Former Alert
ALERT For Hazardous Road Conditions Late Monday Into Tuesday Morning, Especially On Secondary Roads At Middle To Upper Elevations
Much colder air will pour into the mountain area Monday afternoon into Tuesday, with bitter wind chills and a prolonged period of below freezing air temperatures expected ( Monday into Thursday ) at middle to upper elevations.
Rain showers will change to snow showers-flurries Monday afternoon, with accumulating snow levels dropping from upper elevations into middle-lower elevations by late Monday into Monday night.
*A Snow Squall potential will exist by later Tuesday into Tuesday evening, with bursts of intense snow becoming possible. An alert for hazardous travel conditions may be needed.
*A prolonged rime formation event is expected at upper elevations across the High Knob Massif starting Monday afternoon and extending into the predawn to morning hours of Wednesday ( November 28 ).
*Strong & gusty SW-WSW winds are expected at mid-upper elevations late Thursday into Friday as milder air pushes into the mountain area ( sensible warming will be offset by increased wind chills ).
Mountain Area Forecast Details
Overnight Into Monday Morning
Windy with rain showers. A period of downpours possible. Winds S-SW at 10-20 mph, with higher gusts, at elevations below 3000 feet. S-SW winds 15-30 mph, with higher gusts, on mountain ridges above 3000 feet. Widespread temps in the 40s, with 30s at high elevations toward morning. Dense fog ( orographic clouds ) at upper elevations. Wind chills dropping into the 20s & 30s ( coldest highest elevations ) into morning. Light winds in sheltered valleys will give way to strong wind gusts into morning.
Mid-Morning Monday Through The Afternoon
Windy. Turning much colder. Rain showers changing to snow showers & flurries. Low clouds. Riming developing at upper elevations. Winds WSW to WNW at 10-25 mph, with higher gusts. Temperatures falling through the 30s at low-middle elevations and through the 20s at upper elevations. Wind chills dropping into the 20s & 10s, except single digits to near 0 degrees at high elevations by late.
Monday Night Into Tuesday Morning
Snow showers & flurries. Windy & unseasonably cold. Winds W-NW at 5-15 mph, with higher gusts, below 2700 feet. W-NW winds 10-20 mph, with higher gusts, above 2700 feet. Temperatures dropping into the mid 10s to the middle 20s ( coldest at highest elevations ). Wind chills in 10s, except single digits above and below zero at the upper elevations. Riming at upper elevations.
Tuesday Afternoon-Evening
Cloudy with a chance of snow showers-flurries. Local snow squalls becoming possible ( bursts of intense snow ). Winds W-WNW at 10-20 mph, with higher gusts. Temperatures in the 20s to near 30 degrees at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide and in the 10s to lower 20s at upper elevations. Wind chills in the 10s to lower 20s, except single digits to low 10s at the upper elevations. Riming at high elevations.
Overnight Into Wednesday Morning
Snow showers-flurries and light snow. Unseasonably cold. WNW-NW winds 5-15 mph with some higher gusts. Temps varying from single digits at high elevations to the 10s to near 20 degrees. Wind chills in single digits to low 10s at lower-middle elevations and 0 to -15 below zero at upper elevations ( coldest in gusts at highest elevations ).
Mid-Morning Wednesday Through The Afternoon
Flurries ending. Becoming partly to mostly sunny. Cold. Some increase in high clouds possible by late. W to WNW winds at 5-10 mph with some higher gusts. Temperatures varying from lower 20s to the lower 30s ( coldest at the highest elevations ). Wind chills varying from the 20s at low-middle elevations to the 10s ( single digits in gusts on highest peaks ).
*Seasonally cold weather will dominate conditions during Thanksgiving Week across the mountains.
*Rain showers Monday night will give way to snow showers & flurries into Tuesday as air turns colder.
*Although only light snow amounts are expected, I do expect sticking at high elevations and another period with significant rime formation Tuesday (via moisture capture by trees) into early Wednesday within upper elevations, above 3000 feet, in the High Knob Massif.
Rime Covered Northern Slopes of High Knob Massif – November 14, 2018
*The potential for major storm development is being monitored for the final days of November into early December. Stay tuned for later updates.
Mountain Area Forecast ( Nov 18-21 )
Sunday Night Into Monday Morning
Partly-mostly cloudy (mid-high clouds). SSW-WSW winds at 5-15 mph along mid-upper elevation mountain ridges. Temperatures varying from lower 30s to the lower 40s, except locally colder within sheltered mountain valleys. Wind chills generally in the 30s, except 20s in gusts on highest peaks.
Monday Afternoon
Increasing and lowering clouds with a chance of rain showers, especially by late. Winds S-SW at 10-20 mph with higher gusts ( winds may gust over 30 mph along the higher mountain ridges ). Temperatures varying from 40s in upper elevations to the mid-upper 50s in downslope locations of northern Wise and Dickenson counties. Wind chills in the 30s to lower 40s at higher elevations.
Monday Night Into Tuesday Morning
Rain showers developing. Turning colder. Rain showers will change to snow showers at high elevations by morning. Winds SSW-SW at 5-15 mph, with higher gusts on mountain ridges and plateaus below 2700 feet. Winds SW-W at 10-20 mph, with higher gusts, on mountain ridges above 2700 ft. Winds shifting WNW-NW by morning. Clouds lowering to obscure higher mountain ridges. Temperatures falling into the 30s to around 40 degrees, except to around 30 degrees on highest peaks, by morning. Wind chills in the 20s & 30s, except dropping into 10s on high peaks by morning.
Tuesday Morning Through The Afternoon
Low clouds & cold. A chance of drizzle, flurries, and snow showers. Orographic clouds with dense fog-riming at high elevations. Winds WNW-NW at 5-15 mph with some higher gusts. Temperatures nearly steady to slowly falling in the 30s at lower-middle elevations along and west to north of the High Knob Massif-Tennessee Valley Divide, and into 20s at upper elevations. Wind chill factors in 20s to around 30 degrees, except 10s to lower 20s at high elevations.
Tuesday Night Into Wednesday Morning
Mostly cloudy & cold. Winds W-WNW at 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Riming continuing at high elevations. Temps dropping into the 20s to around 30 degrees, except around 20 F at high elevations. Wind chills in the 10s & 20s along mid-upper elevation mountain ridges, with single digits on highest mountain ridges and peaks.
Holiday Season Discussion
This week marks the official beginning of the holiday season, with a passing early week front expected to turn conditions colder prior to Thanksgiving day…but nothing like appears to be upcoming to close out November 2018.
Looking From High Country of Rime Covered Big Cherry Lake Basin
This chilly trend shows up on the 5-day mean charts from the European Model and its 51-member ensemble group; although, some moderation follows briefly the extended trend is looking to turn sharply colder.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
November 20-22 will be the coolest days in this period, especially Tuesday into Wednesday ( November 20-21 ), leading up to Thanksgiving day.
Brief moderation is then looking to be followed by an active pattern which turns sharply colder during the final days of November into early December ( to emphasize this again ).
European Model 850 MB Temperature Anomalies Forecast: Days 1-5
Some late week-weekend moderation is currently expected ahead of what looks to be an interesting period to finish out November and open December 2018 ( are you beginning to sense that I am trying to shift your focus toward the week after Thanksgiving ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
Ridging across Greenland is expected to aid increasingly negative AO and NAO teleconnections, which with a trend toward an increasingly +PNA after November 24 will act to bring wintry conditions into the mountain region. If the EPO also trends negative, as currently suggested, that will up the ante for some serious winter weather.
ALERT For Ice Storm Conditions At Upper Elevations In The High Knob Massif Through Thursday Morning
Caution is advised for those living and traveling across the High Knob Massif, especially at upper elevations above 3000 feet on State Route 619, 706, Routes 237, 238, 704 & others in the high country. Breaking tree limbs and locally downed trees will be a threat.
Major Ice Storm on Eagle Knob – Cody Blankenbecler Image At 10:50 AM
Major ice storm conditions are revealed in wake of overnight freezing rain, with a mid-morning change to snow on the 4196 foot summit of Eagle Knob of the High Knob Massif. Note bent and drooping trees.
ALERT For Strong Rises On Streams Into Thursday PM
While freezing rain and icing is holding back some water, a strong rise is expected on creeks draining the border area of Wise-Scott-Lee counties and adjacent counties along the Cumberland Mountains. Caution is advised.
*A pocket of cold air aloft will move across the mountains late Thursday into Friday morning to change all lingering precipitation into snow and slowing down run-off.
Expect light accumulations of snow, with a dusting up to 2″ by Friday morning (generally heaviest at upper elevations).
Former Alerts
ALERT For DENSE Fog Formation With Dropping Cloud Bases Tuesday Into Tuesday Night For Locations Along And North Of The High Knob Massif-Tennessee Valley Divide On Northerly Upslope Flow. Caution is advised.
Cloud bases will likely drop as low as the Town of Wise, on northerly upslope flow, with levels as low as 2000 to 2500 feet being possible. As typical, temperatures will remain milder well below cloud bases in downslope locations of the Clinch, Powell & Holston valleys southeast into the TRI area ( Great Valley and Tri-Cities ).
ALERT For Freezing Fog Beginning At Elevations Above 3500 Feet By 10 AM Tuesday — With Dropping Freezing Levels To 2500 Feet By 7-10 PM Tuesday
Dropping temperatures Tuesday will allow the freezing level to slowly decline from upper into middle elevations during the mid-morning to mid-evening period. Riming is only expected to be significant at upper elevations.
Weather Headlines ( November 11-15 )
*Another significant weather system will begin impacting the mountain area by Monday afternoon into Monday night, with widespread rain.
*Strong rises on creeks draining the High Knob Massif will be possible into Tuesday, where recent rainfall has been significant during November.
*Expect falling temperatures Tuesday as winds shift NW-N with readings dropping into the 20s to lower-middle 30s during mid-late afternoon. Cloud bases will obscure elevations above 2500 to 3000 feet.
*A new upper wave renews rainfall by the overnight-to-predawn hours of Thursday, with significant rain amounts. In addition, icing with freezing rain will also be possible in upslope zones along the High Knob Massif and windward slopes of the Tennessee Valley Divide prior to changing into rain Thursday AM.
Strong rises on streams are expected with saturated conditions already existing, raising the potential of localized flooding. Creeks draining the High Knob Massif are expected to ROAR into the afternoon.
*A pocket of cold air aloft could support a change to snow by later Thursday into Friday morning with the first widespread, light snow accumulations.
Mountain Area Forecast ( Nov 13-15 )
Overnight Into Tuesday Morning
Low clouds, with areas of fog. Rain redeveloping overnight into the morning. Winds becoming WNW-NNW at generally less than 10 mph. Temperatures holding near steady in the 40 to 45 degree range. Wind chills in the 30s to lower 40s.
Mid-Morning Tuesday Through The Afternoon
Turning colder. Lowering cloud bases with dense fog at mid-upper elevations ( generally above 2000-3000 feet ). Freezing fog developing at high elevations, with dropping freezing levels through the afternoon. Nasty and cold with a chance of light showers-drizzle or mixed precipitation. Winds NW-N at 5-15 mph with higher gusts, especially at higher elevations. Air temperatures falling through the 30s ( into 20s at high elevations by mid-late afternoon ) in locations along & north of the High Knob Massif-Tennessee Valley Divide. Wind chills falling into the 20s, with 10s at highest elevations, during mid-late afternoon.
Tuesday Night Into Mid-Morning Wednesday
Low clouds-dense fog and freezing fog. Chance of flurries or drizzle-freezing drizzle. Cloud bases will try to lift and break during the overnight to mid-morning period. Winds NNW-NNE at 5-15 mph. Cold with temperatures varying from upper 10s to upper 20s ( coldest at upper elevations ). Wind chills in the 10s to lower 20s on exposed mountain ridges and plateaus ( single digits possible in gusts on highest peaks ).
Wednesday Afternoon
Partly-mostly cloudy (mid-high clouds). Unseasonably cold. NE-E winds at 5-15 mph, with some higher gusts. Temperatures in the 30s to near 40 degrees. Wind chills in the 20s to lower 30s ( coldest at highest elevations ).
Wednesday Night Into Thursday Morning
Rain developing, with freezing rain possible ( most widespread at upper elevations in the High Knob Massif ). Low cloud bases with dense fog at upper elevations. Winds ESE to SSE at 10-20 mph with higher gusts along mountain ridges. Cold with temps in the 30s, except around freezing in colder locations. The temperature will tend to rise into the overnight to mid-morning in locations receiving an increase in downslope flow on ESE-SSE winds.
Weather Discussion ( NASTY )
A simply nasty weather pattern is gripping the mountain region. Precipitation began in frozen forms, with freezing temps, at highest elevations within the Cumberland Mountains on Monday (*).
*Especially atop the High Knob Massif and on the peak of Black Mountain, with mixed precipitation amid evaporative cooling.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Initial column cooling was supported by evaporation to drop air temperatures to around freezing during the first hour or two of precipitation, with Doppler radar bright banding also indicating this period aloft.
Black Mountain Mesonet – Ending At 1:15 PM on November 12, 2018
Tuesday is going to be an even nastier day in terms of dropping temperatures and a damp, bone-chilling feel to the air. Low-level moisture convergence and a drop in cloud bases along and north of the lifting zone of the High Knob Massif-Tennessee Valley Divide will support the worst, most nasty conditions.
NAM Model 850 MB Temp-Air Flow Forecast At 7 PM Tuesday – November 13, 2018
A rather classic orographic upslope flow-adiabatic cooling setting is being forecast Tuesday on weak cold air advection into slopes facing inflowing air along the Cumberland-Allegheny Front.
A prolonged period of riming will occur at high elevations as air temps drop to freezing by mid-morning Tuesday at elevations above 3500 feet. The freezing level will then decline through the afternoon, eventually dropping to around or below 2500 feet during Tuesday evening.
NAM Model Forecast Sounding At 4 AM Thursday – November 15, 2018
The next main weather problem develops late Wednesday into Thursday morning, with a strong low-level inversion supporting cold air below 5000 feet. With ESE to SSE flow this type of atmospheric sounding often supports icing in upslope locations of the High Knob Massif, and along the eastern slopes of the Blue Ridge.
The remainder of the area will have temperatures at or above freezing, with a rising tendency as winds downslope more strongly into Thursday morning.
The icing threat will then diminish in the High Knob Massif and along the Blue Ridge as Thursday progresses and winds change direction in advance of a strong upper-level wave ( below ).
NAM Model 850 MB Temp-Air Flow Forecast At 7 PM Thursday – November 15, 2018
A pocket of cold air aloft associated with an upper-level low and strong PVA ( positive vorticity advection ) will support the potential of the first widespread snow accumulation during Thursday evening into early Friday.
NAM Model 500 MB Vorticity Forecast At 7 PM Thursday – November 15, 2018
Amounts of 1″ to 3″ will be possible, but stay tuned for later updates on this first widespread sticking of the season.
The coldest temperatures of this young 2018-19 cold weather season were observed into Saturday morning, November 10 at high elevations, and Sunday morning within mountain valleys. Although skies cleared after some flurries and snow showers, conditions continued changing and interacting with complex terrain.
High Knob Massif Webcam – University of Virginia’s College At Wise
MIN temperatures fell into the 10s at high elevations in the High Knob Massif into Saturday morning, with 0 degree or lower wind chills in gusts on highest peaks.
The atmospheric setting began changing late Saturday into Sunday morning, with dry air & warm air advection at high elevations supporting cold air drainage and a temperature plunge into mountain valleys.
Black Mountain Mesonet At 6:55 AM on Sunday – November 11, 2018
Temperatures actually rose Saturday night into Sunday AM at high elevations, with 30 degrees reported by the mesonet site on Black Mountain at 6:55 AM Sunday (above). This was down from 32 degrees just over an hour earlier. MAX temps during Saturday, by contrast, held in the 20s all day at high elevations in the High Knob Massif and Black Mountain.
Norton Elementary School Weatherbug At 6:55 AM on Sunday – November 11, 2018
At the same time, 6:55 AM Sunday, a temperature of 17 degrees was reported by the Weatherbug site at Norton Elementary School; however, it should be noted that the actual air temperature at 5 feet above ground level was in the 14 to 15 degree F range ( the Norton ES sensor is 15-20 feet above ground level next to the school roof and above large asphalt areas instead of natural surfaces ).
Minimum Temperature Reported In Burkes Garden – Sunday – Nov 11, 2018
Minimum temperatures fell into upper single digits to lower 10s in colder mountain valleys from the High Knob Massif to Burkes Garden, at elevations above 2700-3000 feet, with 11 degrees officially in Burkes Garden.
That is the way to nail down a temperature forecast within complex terrain ( a couple days ahead of time )!
The first of two significant blasts of cold air will begin to push into the Appalachians late Friday into Friday night, with rain giving way to a chance of flurries and snow showers ( especially along the upslope side of the mountains on WNW-NW air flow trajectories ).
Unseasonably cold air is expected during Saturday into Sunday morning as skies clear, with deep blue, polar-arctic air as dewpoints tumble.
Single digit to below zero wind chills will develop at highest elevations later Friday night into Saturday morning. Caution is advised for anyone hunting or planning to be outdoors for any length of time.
This sets the stage for near record to record level cold into Sunday morning, especially in mountain valleys, with temperatures in the 10s and 20s ( rising through the 20s to near 30 degrees F at highest elevations to contrast with the potential of single digits in upper elevation mountain valleys ).
*Coldest single digit temperatures will be possible in colder valleys from the High Knob Massif to Burkes Garden within southwestern Virginia. Note these are actual air temps and not wind chills (with cold air drainage and near calm wind).
Another significant weather system is expected next week, with a much better potential for accumulating snow as an even colder blast of air strikes by later Tuesday into Wednesday AM ( November 13-14 ).
A zonal continental flow field is expected to develop, with much milder conditions, later next week into the weekend of November 17-18.
Mountain Area Forecast
Friday Morning Into The Afternoon
Significant rain develops Friday with a temperature fall beginning during mid-late afternoon as winds shift WNW-NW at 10-20 mph.
Friday Night Into Saturday Morning
Sleet, flurries and snow showers develop Friday night into Saturday morning. Accumulations of a dusting up to 1″ will be possible ( especially upper elevations ). Little to nothing along lee side of mountains.
Gusty WNW-NW winds at 10-20 mph, with higher gusts will generate nasty wind chills. Temperatures fall into mid-upper 10s to the mid-upper 20s ( coldest at highest elevations ), with wind chills varying from 10s to lower 20s below 3000 feet to the single digits and 10s at elevations above 3000 feet ( around or below 0 degrees in gusts on highest peaks ).
Rime formation expected at elevations above 3000 to 3300 feet as temperatures fall below freezing amid orographic clouds.
Saturday Morning Through The Afternoon
Saturday morning clouds and any flurries give way to clearing, with deep blue skies. Unseasonably cold for early November with temperatures varying from 20s at upper elevations to the low-mid 30s (20-25 degree max temperatures at highest elevations).
NW-N winds at 5-15 mph will produce wind chills in the 10s & 20s, to near 30 degrees at lower elevations, except 0 to 10 degrees in gusts during the morning at highest elevations. Milder conditions expected into lower elevations of the Clinch, Powell, and Holston valleys on downslope flow.
Saturday Night Into Sunday Morning
Expect mostly clear and unseasonably cold conditions Saturday night into Sunday morning. A large vertical temperature spread is expected to develop between exposed ridges-plateaus and bitter valleys. Min temps will vary from 10s in valleys ( single digits likely in coldest valleys at upper elevations ) to slowly rising readings through the 20s to around 30 degrees at highest elevations by Sunday AM.
Weather Discussion (Early Winter)
Friday Afternoon Update
High Knob Massif Webcam – University Of Virginia’s College At Wise
Low clouds bases, obscuring elevations above 2800 to 3000 feet, marks the beginning of a significant temperature drop through Friday night into Saturday morning.
Although some flurries and snow showers will develop, the main story will be the cold as wind chills fall to dangerous levels for those unprepared for this early blast of winter. This will be especially true for those living and traveling across middle-upper elevations above 2000-3000 feet.
Previous Discussion
A early winter weather pattern will dominate the mountain landscape through coming days, with only a brief break in between these first two blasts of early season polar-arctic air.
Looking SE Across The Crest of the High Knob Massif – November 3, 2018
More and more trees will become bare in coming days, with peaks observed during October 15-25 above 3000 feet and during October 25-November 5 at elevations below 3000-3200 feet ( unusually late ).
Lower North Slopes of High Knob Massif on November 3, 2018
The first accumulating snow and rime was featured into early hours of November 3.
Rime Coated Cow Parsnip At Upper Elevations – High Knob – November 3
*Frosty cold conditions are expected, especially in mountain valleys, on Wednesday-Thursday mornings in advance of the first of two important weather systems.
*Winds become gusty Thursday night with rain developing into Friday morning. Low clouds, wet, chilly conditions are expected Friday at high elevations and across the area for much of this weekend into Monday.
*Unseasonably cold conditions with slowly dropping temps Saturday will mark the start of a period with much below average conditions which extends into early Tuesday. The days of October 27 and October 29 are looking coolest in the short-term, with October 29 expected to modify more by late in the day than previous model runs indicated.
*A warmer break is expected for Halloween ahead of huge, cold upper-air trough development over North America as Hurricane Yutu recurves and becomes absorbed into the Polar Jet Stream at higher latitudes. Stay tuned for later details on how this will impact local conditions.
Overnight Into Wednesday Morning
Clear & cold. Winds NNW-NNE at 5-10 mph, with some higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from lower-middle 20s to the low-mid 30s ( coldest in upper elevation valleys ). Wind chill factors in the 20s & 30s ( coldest highest ridges ).
Wednesday Afternoon
Mostly sunny ( few high clouds possible ). Blue skies. Seasonally chilly. Light N to NE winds generally less than 10 mph. Temperatures varying from the low-mid 40s to the lower-middle 50s ( coolest at upper elevations ).
Wednesday Night Into Thursday Morning
Mostly clear, then increasing high clouds into morning. Large vertical temperature difference developing between colder mountain valleys & milder ridges-exposed plateaus. Light winds. Temperatures varying from the lower 20s to the lower-mid 40s on exposed ridges-plateaus ( 10s possible locally within high valleys from the High Knob Massif to Burkes Garden ).
Thursday Afternoon
Increasing and thickening high to mid-level clouds. Chilly. Generally light winds. Temperatures in the 40s to lower-mid 50s, coolest in upper elevations.
Thursday Night Into Friday Morning
Increasing & lower clouds with rain developing overnight into morning. Becoming gusty. Winds SE-SSE at 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. Winds SE-S at 10-20 mph, with higher gusts, mountain ridges above 2700 feet. Chilly with temperatures dropping into the upper 30s to middle 40s ( coolest high elevations ). Low clouds with dense fog at upper elevations. Wind chills in the 20s & 30s on mid-upper elevation ridges.
Friday Morning Through The Afternoon
Morning rain, tapering to showers or drizzle into the afternoon. Low clouds and areas of fog. Winds SE to S at 10-20 mph, with higher gusts in mountain wave zones of Powell Valley and the Clinch River Valley. Winds SSE-S at 20-30 mph, with higher gusts above 2700 feet (winds may gust over 40 mph at high elevations & in breaking waves ). Temperatures varying from low-mid 40s to low-mid 50s (coolest at upper elevations). Wind chills in the 20s & 30s at high elevations.
Circulation around the first Nor’easter of the season will be driving a W-NW upslope flow Saturday into Sunday morning across the mountains. Most places will see rain showers-drizzle, but some snow will be mixing in at high elevations. A small accumulation will be restricted to highest peaks, with riming also possible amid clouds.
Saturday Morning Through The Afternoon
Periods of showers & drizzle. Low clouds and dense fog at upper elevations. Showers may mix with or change to snow highest elevations. Winds W-NW at 10-20 mph with higher gusts on mid-upper elevation ridges. Temperatures steady to slowly falling through the 40s at low-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide and through the 30s at upper elevations. Wind chills in the 30s and 20s on higher mountain ridges.
Saturday Night Into Sunday Morning
Periods of showers & drizzle. Snow showers-flurries at highest elevations. Low clouds with dense fog at upper elevations. Winds W-NW at 5-15 mph with higher gusts on middle-upper elevation ridges. Temperatures varying from lower 30s to lower 40s ( around 30 degrees highest peaks ). Wind chills in the 30s & 20s, except 10s in gusts on peaks above 3600 feet.
Weather Discussion ( Winter Pattern )
Although autumn color is peaking ( nearing or past ) at upper elevations in the High Knob Massif, a pattern more like winter will be developing in coming days.
Autumn Color On Northern Slopes of High Knob Massif
Conditions deteriorate into Friday as remnants of former Hurricane Willa get absorbed into the upper-level flow and a new low pressure lifts northeast out of the Gulf of Mexico.
Sunset From The High Knob Massif – October 18, 2018
Although the track of this Gulf low will be right for snow, temperatures will remain a little too warm; although, the conditions will be simply nasty and unseasonably chilly.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 3-7
A deep, winter-like upper-level trough digs into the region in wake of this first nasty system, with really cold air, more showers and a chance for some snow ( especially at higher elevations ) as temperatures go sub-freezing.
*The first snowflakes of this 2018-19 cold season fell at the summit level of the High Knob Massif during early hours of October 21. The first riming also briefly developed. Wind gusts to around 50 mph blasted the high summits prior to arrival of the coldest air into predawn hours of Sunday.
European Model 850 MB Temperature Anomalies Forecast: Days 4-8
The European Model is forecasting mean temperatures to hover around freezing during the final days of October at the summit level of High Knob, which translates to some unseasonably cold conditions at middle-lower elevations.
Frost will become widespread across the area by overnight into Thursday morning.
Due to breezy-gusty northerly winds, sites exposed within middle elevations will have less frost than more sheltered locations (temperatures at high elevations will still reach freezing even with wind). Fog will be likely along major river valleys and lakes.
*ALERT For Freeze Within Mountain Valleys – Coldest Temperatures Expected During Thursday Night Into Friday Morning
Frost will be patchy to widespread in mountain valleys and limited to none across exposed mountain ridges as a notable temperature inversion develops. The coldest temperatures of this initial chilly shot will occur in mountain valleys during Thursday night into Friday morning.
Fog will be possible again along major river valleys, with latent heat of condensation offering protection from the colder air expected in valleys with little to no fog.
Colder mountain valleys will have a hard freeze, with the coldest air expected in upper elevation valleys from the High Knob Massif to Burkes Garden due to very low dewpoint air and drainage into high valleys.
*First Widespread Freeze This Weekend
The first true blast of winter-like air will arrive this weekend with falling temperatures Saturday and unseasonably cold air Sunday ( October 21 ).
This blast of air will support the first widespread freeze, with even milder river valleys likely to dip below freezing.
Temperatures are likely to remain below freezing all day Sunday at upper elevations, with temps struggling in the 30s at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide. Potential for the first sticking snow is also being monitored for Sunday Morning, especially at upper elevations. Stay tuned for updates.
Former Alerts
ALERT For Dropping Cloud Bases And Dense Fog On Upsloping Northerly Winds At Mid-Upper Elevations Along & North Of The High Knob Massif-Tennessee Valley Divide For Later Monday Night Into Tuesday
A wind shift behind a cold front will combine with lingering low-level moisture under a developing inversion to develop dense fog at mid-upper elevations along and north of the High Knob Massif-Tennessee Valley Divide later Monday evening into Tuesday. Caution is advised.
Weather Headlines
*Raw, damp & chilly conditions are expected Tuesday in advance of a dewpoint front that will scour out abundant low-level moisture by Wednesday.
*The first widespread frost and freeze of the season is expected to develop Wednesday Night into Thursday Morning, with temperatures dropping into the 20s to around 30 degrees in most locations. Protective fog will be possible along major river valleys-lakes.
Upper air ridging will be building over the western USA as a deep trough develops over the northeastern USA in coming days. Note a split flow pattern. A developing central-Pacific based +ENSO, also known as a Modoki El Nino, will be a significant player in weather conditions expected during Winter 2018-19.
*A below average temperature pattern is generally expected to dominate the remainder of October, with up-down swings during frequent frontal passages.
Monday Night Into Tuesday Morning
Rain showers. Turning cooler with dropping cloud bases and dense fog formation at elevations around and above 2500 feet ( along and north of the High Knob Massif and Tennessee Valley Divide ). Winds shifting NNW to NNE at 5-15 mph with higher gusts. Temperatures dropping into the 40s ( around 40 degrees at high elevations ). Wind chills falling into low 30s to low 40s ( coolest high elevations ).
Tuesday Morning Through The Afternoon
Low clouds & chilly. Chance of rain showers. Light winds becoming SW at 5 to 15 mph, with higher gusts, by late, on middle-upper elevation mountain ridges. Temperatures in the 40s to lower 50s. Wind chills in the 30s higher ridges.
Tuesday Night Into Wednesday Morning
Mostly cloudy (mid-high clouds following dissipation of low clouds). Chance of a shower or sprinkles early. Areas of fog possible in valleys. Winds W-NW at 5-15 mph, with higher gusts. Temperatures in the mid 30s to middle 40s. Wind chills dropping into the lower 30s to around 40 degrees.
Wednesday Afternoon
Mostly sunny, blue skies (some high clouds possible). Crisp and breezy to gusty. WNW to NW winds 10-20 mph with higher gusts ( especially mountain ridges ). Temperatures in the upper 40s to lower 60s, coolest at upper elevations.
Wednesday Night Into Thursday Morning
Clear & cold. Frost and sub-freezing conditions becoming patchy to widespread. Fog possible in major lake and river valleys. Breezy to gusty NNW-NNE winds diminishing to generally less than 10 mph into morning. Temperatures dropping into the mid 20s to the low-mid 30s ( coldest in high mountain valleys and on highest mountain ridges ).
Thursday Afternoon
Sunny. Blue skies. Light & variable winds. Temperatures varying from low-mid 40s to the low-mid 50s ( coolest in upper elevations ).
Thursday Night Into Friday Morning
Mostly clear. Frosty cold valleys. A large vertical temp spread developing between colder valleys and exposed plateaus-ridges. Light SSE-SW winds along mid-upper elevation mountain ridges. Fog along major river valleys.
Temps varying from the 10s to middle 20s in colder valleys to the middle-upper 30s on exposed portions of mountain ridges and plateaus.
