Forest fire conditions will worsen as the pressure gradient increases in advance of a cold front by late Thursday Night into Friday Night, before easing with increasing moisture, rising RH-cold air, this weekend.
A sharp temperature change will occur between Friday Night and Saturday afternoon-evening, with falling temperatures during the day Saturday ( and much colder wind chill factors ). Flurries and snow showers will be possible Saturday Night into Sunday, especially along the upslope side of the mountains.
Overnight Into Thursday Morning
Mostly clear. Light winds except NW at 5-10 mph along upper elevation ridges. Large vertical temp spread from frosty valleys to exposed ridges. Temps varying from the 20s in colder valleys to the low-mid 40s on exposed ridges.
Thursday Afternoon
Mostly sunny. Mild. Winds SSW-WSW generally less than 10 mph. Temperatures varying from upper 50s to lower 60s in upper elevations to the middle 60s to around 70 degrees ( warmer south into the Great Valley ).
Thursday Night Into Friday Morning
Mostly clear. Large vertical temperature spread forming between colder valleys and mild ridges. SSW to WSW winds 5 to 15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from 20s to mid 30s in colder valleys to the upper 40s to mid 50s on ridges.
Friday Afternoon
Mostly sunny. Unseasonably warm. SSW-SW winds 5-15 mph, with higher gusts. Temperatures varying from lower-middle 60s in upper elevations to the upper 60s to lower 70s ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
Mostly clear early with increasing clouds and developing rain showers by morning. Becoming windy. SSW-SW winds increasing to 10-20 mph, with higher gusts, below 2700 feet by morning. SW winds at 15-25 mph, with higher gusts, on middle-upper elevation mountain ridges above 2700 feet. A large vertical evening temperature spread forming between colder valleys and breezy-gusty ridges, then temps rising in valleys overnight into morning ( falling on high ridges into morning ). Evening temps falling into 30s & 40s in valleys versus 50s-lower 60s on ridges. High ridges dropping rapidly to around 40 degrees by morning.
Saturday Morning Into Saturday Afternoon
Turning sharply colder. Morning rain showers possibly mixing with or changing to snow in upper elevations before ending. Windy. W-NW winds 10-25 mph, with higher gusts. Temperatures falling into the 30s by afternoon at middle-lower elevations, and into the 20s at upper elevations, in locations along & north-northwest of the High Knob Massif and Tennessee Valley Divide. Wind chills dropping into the 10s and 20s ( except some single digits possible on highest peaks above 3500 feet ).
Flurries & snow showers will be likely Saturday Night Into Sunday along the upslope side of the mountains, with light accumulations ( up to 1″ possible at highest elevations ). Formation of rime along the highest ridges and peaks ( above 3500 ft ) is expected.
*Note To Hunters: A prolonged period of sub-freezing conditions will occur from mid-morning Saturday into Monday above 3000 feet in the High Knob Massif. Bitter wind chill factors will also accompany the cold from Saturday into Sunday, especially on mountain ridges. Some slick stretches will be possible on roads within highest elevations as well.
Weather Discussion ( Wintry Blast )
The first blast of true winter air will strike Saturday with plunging temperatures and wind chills behind a cold front that passes early in the morning.
Forest Fire In SE Kentucky – Viewed From Pine Mountain In Dickenson County
Worsening fire conditions will have to be respected in advance of this cold front during Friday into Friday Night as winds increase with a strengthening pressure gradient. Smoke from many large fires burning across the southern Blue Ridge into the Cumberland Plateau may increase as winds shift S-SW in advance of this front.
NAM 12 KM Model Total Precipitation Forecast
Significant precipitation has never been expected with this event across the southern Appalachians, and latest model runs continue to confirm this with a weakening trend in precipitation amounts from west to east ( with little to nothing reaching east of the mountains ).
NAM 12 KM Model 850 MB Wind & Vorticity Forecast – 7 AM Sunday
It is hoped that enough moisture will be tapped from the Great Lakes to carry some into the southern Appalachians, with models suggesting best chances being northeast of the Great Smokies during Saturday Night into Sunday ( forcing from orographics will be moderate-strong with moisture seen as the limiting factor at this point ).
Some riming and light snow will be possible along windward slopes and crest lines in the High Knob Massif and Mount Rogers-Whitetop areas, with more significant snow accumulations to the northeast atop the eastern highlands of central-northern West Virginia. A small southward shift of air flow trajectories could change this, so be sure to check back for updates to see if local amounts may be greater than currently suggested by models.
As might be expected, the Great Lakes have unseasonably warm water for this time of year so if the vertical temp gradient can generate more mixing than models perceive ( via cold air moving over warm water ) then down-stream amounts could be greater than indicated in upslope locations.
