*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.
