ALERT For Strong ( ROARING ) SW Winds Developing On Middle-Upper Elevation Mountain Ridges-Plateaus During Tuesday Night Into Wednesday
An increasing pressure gradient will develop strong SW winds along the Cumberland Mountains late today into Wednesday AM. Mixing of ROARING SW winds into lower elevations northeast of the High Knob Massif-Tennessee Valley Divide will also be possible for locations in the Pound-Clintwood corridor, for example, of the Russell Fork Basin as vertical mixing increases. The magnitude of downward mixing will be hindered if a very strong inversion can develop in lower levels; however, it is not currently expected to be deep enough to greatly hinder downward mixing in favored sites.
In general the strongest winds are expected for exposed locations from Norton-Wise upward in elevation during Tuesday Night into Wednesday morning as a low-level jet at 875-850 MB develops and lowers, with topographic channelization, between the High Knob Massif and Black mountains along the High Knob Landform.
Tonight Into Tuesday Morning
Mostly clear. Frosty mountain valleys with a hard freeze. W to SW winds at 5-15 mph, with higher gusts, on exposed middle to upper elevation mountain ridges and plateaus. Temperatures varying from low-mid 20s colder valleys to low-mid 30s on exposed middle elevation ridges ( except upper 10s-lower 20s in coldest mountain valleys of the middle-upper elevations ). Wind chills in the 10s & 20s along higher mountain ridges.
Mostly sunny. Milder. Winds SSW-SW at 5-15 mph, with higher gusts. Temperatures varying from upper 40s to low 50s at upper elevations ( above 3000 feet ) to the upper 50s to lower-mid 60s.
Tuesday Night Into Wednesday Morning
Mostly clear. Becoming windy. Large vertical temp spread between mid-upper elevations and any valleys that remain sheltered from strong winds in lower elevations. SSW-SW winds 15-30 mph, with higher gusts, below 2700 ft. Winds SW-WSW 20-35 mph, with gusts to 45+ mph, along ridges above 2700 feet. Temperatures in the 40s to around 50 degrees, except 30s in any valleys that remain decoupled and sheltered from strong winds.
*Wind gusts of 30 to 50+ mph will be possible at middle to upper elevations, and where mountain waves may aid mixing downward into lower elevations northeast of the High Knob Massif-Tennessee Valley Divide during Tuesday Night into Wednesday morning.
Weather Discussion ( March 20-22 )
A cold Palm Sunday weekend was experienced across the Cumberlands, with rime formation at high elevations amid the High Knob Massif into Sunday morning.
The bulk of snowfall remained far northeast and south of the area, with local accumulations at highest elevations up to 7″ on Canaan Mountain, in northeastern West Virginia, and atop Mount LeConte in the Great Smokies ( a trace was reported on Beech Mountain ).
Snowfall was limited to only a trace. This has been a trend with precipitation, in general, during March 2016 which is currently on pace to become the driest March of all-time.
*A predicted band of showers & thunderstorms, with downpours, could change this and, at least, prevent March 2016 from becoming the driest on record by Thursday Night-Friday AM. Time will tell.
Most cultivated and woodland wildflowers currently in bloom across Wise & Dickenson counties are climatized to coldness as typically observed in March. A widespread freeze occurring into Monday morning ( March 21 ) with MIN temperatures in the 20s being common ( upper 10s to lower 20s in the coldest places ).
*Wind chill factors dropped to around 0 degrees, in gusts, atop the High Knob Massif during Sunday night into Monday morning.
The weather focus this week, and actually through the remainder of March into early April, will be on a up-down temperature regime so common at this time of year as the season’s battle for control of the regional landscape.
Although some maples are budding, the majority of trees remain bare and devoid of new growth ( the mid-April to mid-May period being climatologically the explosive period of regeneration and spring renewal across most of Wise and Dickenson counties ).
*Spring growth and renewal tending to occur earlier on the Kentucky side of the stateline, and in river valleys southward toward the Tri-Cities and southwest toward Cumberland Gap, than in most of Wise County.
Clear skies and relatively light winds will set the stage for another cold and frosty morning in mountain valleys, with 18-25 degrees in coldest valleys and upper 20s to lower 30s in milder valleys ( as of 10:30 PM Monday it was already in the upper 20s to lower 30s in colder mountain valleys ).
Dewpoints are very low as this recent air mass was of Arctic origins, late season modified, and are aiding temperatures declines in mountain valleys ( especially ) via drainage and radiational cooling.
Conditions begin changing significantly by late today into Wednesday morning as the pressure gradient tightens up along and west of the Appalachians. A classic ROARING wind setting for the Cumberlands, and I already have an ALERT to cover this so everyone will be aware of these changes upcoming tonight into early Wednesday.
This strong warm air transport will occur in advance of the next chance for rain and thunderstorms by late Thursday into early hours of Friday.
The Storm Prediction Center currently has a slight risk of severe thunderstorms west of the mountains. This area will need to be followed through coming days ( as changes will be likely ).