A period of accumulating snow will be possible late Saturday into Sunday AM ( December 9-10 ), especially in locations along & north-northwest of the High Knob Massif and Tennessee Valley Divide, with a new surge of bitterly cold air.
Overnight Into Tuesday Morning
Becoming cloudy. Windy, especially along mid-upper elevation mountain ridges. Large vertical temp spread through early overnight between sheltered valleys and exposed ridges. SSE-SSW winds 10-20 mph, with higher gusts, below 2700 feet. S to SW winds 15-30 mph, with gusts over 40 mph, on mid-upper elevation ridges. Temps varying from 30s in colder valleys to the mid 40s to mid 50s along mountain ridges & exposed plateaus. Wind chills in the 30s along upper elevation mountain ridges.
Tuesday Morning Through The Afternoon
Cloudy & windy with rain developing. Local downpours. Winds SSW-WSW at 10-25 mph, with higher gusts. Turning cooler by late. Temperatures varying from low-mid 40s to the low-mid 50s. Low cloud bases with dense fog at upper elevations. Wind chills in the 30s along upper elevation mountain ridges.
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. A chance of flurries. Turning colder. Winds WNW to NW at 5-15 mph, with higher gusts. Temps from low-mid 20s to lower 30s. Wind chills in the 10s and 20s, except single digits in gusts at highest elevations.
Wednesday Afternoon
High clouds. Cold. Winds SW-W at 5-10 mph, with some higher gusts. Temperatures varying from upper 20s to lower 30s in upper elevations to upper 30s and lower 40s. Wind chills in the 20s to lower 30s on mountain ridges, except 10s in stronger gusts at highest elevations.
Wednesday Night Into Thursday Morning
Mostly cloudy ( high clouds ) and cold. Winds WSW-WNW at 5-15 mph, with higher gusts. Temperatures widespread in the 20s to around 30 degrees. Wind chills in the 10s & 20s, coldest at highest elevations.
Thursday Afternoon
Partly to mostly cloudy. Cold. Winds WSW-WNW at 5-10 mph, with some higher gusts. Temperatures varying from upper 20s to lower 30s in upper elevations to the upper 30s to lower 40s.
Thursday Night Into Friday Morning
Mostly cloudy. A chance of flurries. Cold. Winds WNW-NNW at 10 mph or less. Temperatures varying from the lower-middle 10s to the low-middle 20s.
A very cold pattern is taking shape for the eastern USA, with this initial push of cold air being only seasonably cold. Increasingly cold air, with potential for extreme cold, is being monitored for this weekend into the next 1-2 weeks in separated surges.
Weather Discussion ( Harsh Potential )
Late Tuesday Evening Update
Only a few changes to this update, including the addition of a word of caution for everyone to be watchful of icy patches on any above ground or outdoor surfaces that remain wet as temperatures continue to drop overnight.
As of Midnight temps had fallen into the middle 20s at highest elevations, in clouds, with wind chills dropping to around or below 10 degrees in gusts ( temps at the summit of High Knob tend to run a couple degrees colder than this live data from the Black Mountain mesonet ).
Black Mountain Mesonet Up To Midnight
Rainfall with Tuesday’s cold frontal boundary averaged 0.75″ to 1.25″ over the High Knob Massif, and along higher portions of the Tennessee Valley Divide, with lesser amounts elsewhere.
The main change to Wednesday is to increase cloudiness, as it looks like it may be difficult to shake the high clouds as tonight’s frontal system stalls far to the south. This will make it a chore for many places to get out of the 30s in upslope locations along and west to southwest of the Tennessee Valley Divide and High Knob Massif.
Previous Discussion
Although only seasonable cold is expected to arrive this week, the upper air flow pattern taking shape across North America during the next 1-2+ weeks has serious potential to turn harsh, with December 1989 being a top analog for this point in time ( differences may; however, result in a varied outcome by January 2018 versus January 1990 ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A majestic sunset graced December 4, with strong S-SW winds at mid-upper elevations being the only negative factor to signal changes upcoming.
Black Mountain Mesonet
These strong winds were putting a chill into the air at high elevations, in the High Knob high country and atop adjacent Black Mountain, where temperatures were in the 40s.
Flatwoods Mountain Mesosnet
Strong winds will continue overnight into Tuesday ahead of a powerful cold front with a band of rain. Winds will tend to mix downward through middle into the lower elevations over time as the front gets closer, with rises in temps being possible in sheltered valleys that decoupled late Monday.
NAM 12 KM Model Total Precipitation Forecast Next 48-Hours
A band of rain, with local downpours, will arrive Tuesday with orographic enhancement of rain being possible from the High Knob Massif and Tennessee Valley Divide south and southwest ( downslope reduction in leeside zones ).
Super Moon – December 3, 2017
I see a progressively colder and more wintry pattern taking shape during the next week to 10 days, with any snow that may eventually fall and accumulate helping to enhance the potential for harsh conditions.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
The upper air pattern taking shape during the next week to ten days is simply classic for increasing cold, with a series of progressively colder air masses likely to impact the region and eastern USA during the next 1-2+ weeks.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
The upcoming pattern is analogous to that observed during December 1989, which featured a 60 degree MAX temp in Clintwood on December 6 prior to the bottom dropping out.
500 MB Height Anomaly Pattern – December 9-29 In 1989
No two seasons are exactly alike, but certainly some do make better analogs than others and December 1989 is a top analog for this current point in time.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
The mean of the European ensemble group has been strongly suggesting that this pattern locks in with a progressively colder nature during the next 1-2 weeks.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10
Although lovers of snow may be disappointed initially, the pattern and ensemble MEAN are also suggesting that snow chances will increase through next week. If snow cover is established then there is NO DOUBT that a pattern like this will turn harsh. Stay tuned for updates.
