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.
