ALERT For Dense Fog Development Into Friday AM For Locations Along and N-NE Of The High Knob Massif & Tennessee Valley Divide
A frontal boundary will drop into the Cumberland Mountains and stall, with fluctuations in its position expected throughout the up- coming weekend. Dense fog will tend to be persistent across high elevations, with intervals of dense fog at middle-lower elevations. Intervals of showers will also occur, continuing this wet pattern.
Overnight Into Mid-Morning Friday
Showers developing. Gusty SW winds shifting NNW-NNE by morning at 5-15 mph, with higher gusts. Dense fog possible, especially at mid-upper elevations along and north of the High Knob Massif-Tennessee Valley Divide. Temperatures dropping into the 40s.
Friday Afternoon
Low clouds. Chilly. Chance of drizzle or light showers. Light & variable winds. Temperatures in the upper 30s to middle 40s in locations along and north of the High Knob Massif & Tennessee Valley Divide ( milder to the south ).
Friday Night Into Saturday Morning
Light rain & showers redeveloping. Areas of fog ( dense at high elevations ). Winds shifting SSW to WSW at 5-15 mph, with higher gusts. Temperatures steady or rising into the middle 40s to lower 50s.
Saturday Afternoon
Showers. Gusty. Areas of fog ( dense at high elevations ). SSW-WSW winds 5-15 mph, with higher gusts, below 2700 feet. Winds SW-WSW 10-20 mph, with higher gusts, along upper elevation mountain ridges. Temperatures varying from upper 40s to upper 50s ( coolest highest elevations ).
Saturday Night Into Sunday Morning
Showers. Area of fog ( dense across upper elevations ). SW-W winds 5-15 mph, with higher gusts, possibly shifting N by morning. Temperatures widespread in the 40s to lower 50s.
*A heavy rainfall potential continues to be monitored for next week. Strong rises on streams could occur depending upon rain amounts. Stay tuned for later updates.
**A major pattern change back to cold, wintry conditions is being monitored for the last week of January into the start of February. Chances for a return to a cold, wintry pattern are increasing for the longer-term period.
Weather Discussion ( Wet Pattern )
A frontal boundary will be dropping into the mountains and stalling, with the boundary being south to north of the area throughout the upcoming weekend. This means periods of showers and a predominance of low clouds, with dense fog being persistent and long-lived across high elevations.
High Knob Massif Webcam – University Of Virginia’s College At Wise
As the front drops into the area by the predawn-morning of Friday the first concern becomes dropping cloud bases and the possibility of dense fog formation amid locations along and north of the High Knob Massif-Tennessee Valley Divide on upsloping northerly winds.
NAM 4 KM Model Temperature Forecast At 10:00 AM Friday – January 13, 2017
The high-resolution NAM Model forecast’s temperatures to drop to around 40 degrees in Wise by 10:00 AM Friday. This would also be accompanied by dense fog. Conditions which actually develop will be highly dependent upon the position of the frontal boundary. The colder air will be shallow, and temperatures at middle-lower elevations north of the High Knob Massif could be cooler than at highest elevations.
NAM 12 KM Model Total Rainfall Forecast To 7 AM Monday – January 16, 2017
Rainfall amounts from Friday through this weekend will also be dependent upon the frontal position. A currently predicted area of heavier rains just north of the area could easily be across the Cumberland Mountains with only a tiny shift in the boundary from current model projections.
*Orographics will also be a factor, such that amounts within the High Knob Massif-Black Mountain corridor are likely to be greater than models are currently forecasting ( as recently observed ).
European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 6 to 10
A continued mild, wet pattern is expected into next week with a combination of Pacific moisture ( at mid-high levels ) and Gulf of Mexico moisture ( at low levels ) setting up the potential for significant rainfall across the Ohio-Tennessee valleys & Appalachians. Timing and details, of course, yet to be resolved ( but the pattern is relatively clear ).
European Model 30 MB Analysis At 7 AM January 12, 2017
Major changes in the stratosphere beyond this upcoming 6 to 10 day period signals an increasing chance for a return of colder, wintry conditions across eastern portions of the USA by the final week of January into early February.
European Model 30 MB Forecast At Day 10: January 22, 2017
*The shift of a developing warm pool of stratospheric air across to the North American side of the North Pole, and eastward shift of the Polar Vortex off the pole, initially suggests a change back toward more typical winter conditions.
If the European group is on target, additional changes in the flow field around the vortex will then set up the return of cross-polar flow back into the USA during early February.
**Although the stratosphere is also dynamic, with many wave influences and interactions, conditions tend to be much more stable than within the troposphere and forecast’s made outward in time also tend to be more reliable than those made within the troposphere. By no means perfect; however, often a usable precursor for upcoming tropospheric changes.
