Frost will become widespread across the area by overnight into Thursday morning.
Due to breezy-gusty northerly winds, sites exposed within middle elevations will have less frost than more sheltered locations (temperatures at high elevations will still reach freezing even with wind). Fog will be likely along major river valleys and lakes.
*ALERT For Freeze Within Mountain Valleys – Coldest Temperatures Expected During Thursday Night Into Friday Morning
Frost will be patchy to widespread in mountain valleys and limited to none across exposed mountain ridges as a notable temperature inversion develops. The coldest temperatures of this initial chilly shot will occur in mountain valleys during Thursday night into Friday morning.
Fog will be possible again along major river valleys, with latent heat of condensation offering protection from the colder air expected in valleys with little to no fog.
Colder mountain valleys will have a hard freeze, with the coldest air expected in upper elevation valleys from the High Knob Massif to Burkes Garden due to very low dewpoint air and drainage into high valleys.
*First Widespread Freeze This Weekend
The first true blast of winter-like air will arrive this weekend with falling temperatures Saturday and unseasonably cold air Sunday ( October 21 ).
This blast of air will support the first widespread freeze, with even milder river valleys likely to dip below freezing.
Temperatures are likely to remain below freezing all day Sunday at upper elevations, with temps struggling in the 30s at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide. Potential for the first sticking snow is also being monitored for Sunday Morning, especially at upper elevations. Stay tuned for updates.
Former Alerts
ALERT For Dropping Cloud Bases And Dense Fog On Upsloping Northerly Winds At Mid-Upper Elevations Along & North Of The High Knob Massif-Tennessee Valley Divide For Later Monday Night Into Tuesday
A wind shift behind a cold front will combine with lingering low-level moisture under a developing inversion to develop dense fog at mid-upper elevations along and north of the High Knob Massif-Tennessee Valley Divide later Monday evening into Tuesday. Caution is advised.
Weather Headlines
*Raw, damp & chilly conditions are expected Tuesday in advance of a dewpoint front that will scour out abundant low-level moisture by Wednesday.
*The first widespread frost and freeze of the season is expected to develop Wednesday Night into Thursday Morning, with temperatures dropping into the 20s to around 30 degrees in most locations. Protective fog will be possible along major river valleys-lakes.
Upper air ridging will be building over the western USA as a deep trough develops over the northeastern USA in coming days. Note a split flow pattern. A developing central-Pacific based +ENSO, also known as a Modoki El Nino, will be a significant player in weather conditions expected during Winter 2018-19.
*A below average temperature pattern is generally expected to dominate the remainder of October, with up-down swings during frequent frontal passages.
Monday Night Into Tuesday Morning
Rain showers. Turning cooler with dropping cloud bases and dense fog formation at elevations around and above 2500 feet ( along and north of the High Knob Massif and Tennessee Valley Divide ). Winds shifting NNW to NNE at 5-15 mph with higher gusts. Temperatures dropping into the 40s ( around 40 degrees at high elevations ). Wind chills falling into low 30s to low 40s ( coolest high elevations ).
Tuesday Morning Through The Afternoon
Low clouds & chilly. Chance of rain showers. Light winds becoming SW at 5 to 15 mph, with higher gusts, by late, on middle-upper elevation mountain ridges. Temperatures in the 40s to lower 50s. Wind chills in the 30s higher ridges.
Tuesday Night Into Wednesday Morning
Mostly cloudy (mid-high clouds following dissipation of low clouds). Chance of a shower or sprinkles early. Areas of fog possible in valleys. Winds W-NW at 5-15 mph, with higher gusts. Temperatures in the mid 30s to middle 40s. Wind chills dropping into the lower 30s to around 40 degrees.
Wednesday Afternoon
Mostly sunny, blue skies (some high clouds possible). Crisp and breezy to gusty. WNW to NW winds 10-20 mph with higher gusts ( especially mountain ridges ). Temperatures in the upper 40s to lower 60s, coolest at upper elevations.
Wednesday Night Into Thursday Morning
Clear & cold. Frost and sub-freezing conditions becoming patchy to widespread. Fog possible in major lake and river valleys. Breezy to gusty NNW-NNE winds diminishing to generally less than 10 mph into morning. Temperatures dropping into the mid 20s to the low-mid 30s ( coldest in high mountain valleys and on highest mountain ridges ).
Thursday Afternoon
Sunny. Blue skies. Light & variable winds. Temperatures varying from low-mid 40s to the low-mid 50s ( coolest in upper elevations ).
Thursday Night Into Friday Morning
Mostly clear. Frosty cold valleys. A large vertical temp spread developing between colder valleys and exposed plateaus-ridges. Light SSE-SW winds along mid-upper elevation mountain ridges. Fog along major river valleys.
Temps varying from the 10s to middle 20s in colder valleys to the middle-upper 30s on exposed portions of mountain ridges and plateaus.