ALERT For Strong SW Winds Into The Overnight In Advance Of Much Colder Air & Snow Squalls
Strong SW winds will continue to ROAR along the Cumberland Mountains into the overnight in advance of a strong cold front. Caution is advised.
ALERT For Accumulating Snow Tuesday With A Sharp Temperature Plunge Through The Afternoon Into The Evening – Low Wind Chills And Hazardous Conditions Are Expected – Especially Along & North to Northwest Of The High Knob Massif and Tennessee Valley Divide
An Arctic Cold Front will push across the mountains Tuesday and will be accompanied by snow showers, flurries, snow squalls and sharply dropping temperatures and wind chill factors. Moderate to strong orographic forcing and increasing instability aloft will create whiteout conditions at times. Widespread snow is expected along and north to northwest of the High Knob Massif-Tennessee Valley Divide, with more scattered activity in downslope locations to the southwest and southeast.
Monday Night Into Tuesday Morning
Partly to mostly clear through the evening, then increasing overnight clouds with a chance of flurries & snow showers developing around sunrise. Windy. Winds SW-W at 15-25 mph, with higher gusts, along mountain ridges & exposed plateaus below 2700 feet. Winds SW to WNW at 20-30 mph, with higher gusts, along mountain ridges above 2700 feet. Rapid evening temperature drop in sheltered valleys, then temps rising overnight with mixing. Turning colder at mid to upper elevations by sunrise. Temperatures dropping into the lower 20s to lower 30s. Wind chills falling into the 10s and 20s, except single digits toward morning on highest mountain ridges.
Tuesday Morning Through The Afternoon
Snow showers, flurries, and snow squalls. A whiteout snow burst possible along the Arctic Front, then hit-miss bursts of heavy snow possible through the afternoon. Windy and turning bitterly cold. WNW-NW winds 10-25 mph, with higher gusts. Temperatures falling through the 20s at middle-lower elevations, and through the 10s at upper elevations above 3000 feet. Wind chills dropping into single digits and 10s in middle-lower elevations and to below zero across upper elevations ( as low as -10 degrees below zero possible on highest peaks by late ).
Tuesday Night Into Wednesday Morning
A chance of snow showers, flurries, and localized squalls through the evening, then partial clearing possible by the predawn to sunrise period. Windy & bitter cold. WNW-NW winds 10-20 mph, with higher gusts. Temperatures in the 10s, with single digits at upper elevations. Wind chills in the 0 to 10 above range at middle elevations and in the 0 to -10 degree below zero range at upper elevations ( except locally -10 to -20 below on highest peaks in gusts ).
Widespread snow accumulations of 1-2″ are expected along and to north-northwest of the High Knob Massif-Tennessee Valley Divide, with locally higher amounts of up to 3″+ in locales experiencing numerous squalls or snowstreaks.
More scattered snow amounts are expected in downslope locations from Big Stone Gap through central-western Lee County, southward into the Great Valley of northeastern Tennessee and southwestern Virginia.
Weather Discussion ( Arctic Front )
A simply gorgeous sunset was observed Sunday following a round of mostly light snow that dropped a dusting to 1″ on the mountain area into early Sunday.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Strong winds and low wind chills over the high country on Sunday were generating an array of nice orographic wave clouds. A few being observed from UVA-Wise near sunset.
High Knob Massif Webcam – University Of Virginia’s College At Wise
High resolution visible imagery Monday revealed lingering snow from the southern snowstorm that dropped rare and impressive amounts of snow far to the south.
Lingering Snow From Southern Storm – December 11, 2017
I have just updated my forecast for an ALERT to cover the Strong SW winds which are roaring across the mountains.
Black Mountain Mesonet For The 1-Hour Period Ending At 8:55 PM ( December 11 )
While strong winds were already in my forecast for tonight, wind speeds at mid-upper elevations have increased above what were predicted earlier, with 40-50+ mph gusts, so an ALERT is needed for locations where many people live.
As often occurs, with mountain wave formation, strong gusts are penetrating down to valley floors in the Pound-Clintwood corridor ( this is not recognized beyond myself so it must not really occur ).
Black Mountain Mesonet For The 1-Hour Period Ending At 7:55 PM ( December 11 )
The main focus beyond these roaring winds tonight will be bitterly cold air pouring into the mountains Tuesday, along with moderate-strong orographic forcing and increasing vertical instability as very cold air aloft steepens the lapse rates through Tuesday afternoon.
NAM 12 KM Model 850 MB Forecast At 10:00 AM Tuesday – December 12, 2017
A WINDEX event is developing into Tuesday and conditions along and west-northwest of the lifting zones of the High Knob Massif and Tennessee Valley Divide, which includes most all of Wise-Dickenson counties, are going to get bad with whiteout conditions at times in addition to plunging temperatures and wind chill factors ( this despite the lack of recognition officially ).
Due to very cold air aloft, some intense squalls may also spill over into the Great Valley.
*Tuesday will be nothing like the Saturday Night into early Sunday period and any forecaster who thinks it will needs to return to school for more training!
