Mountain Area Forecast ( May 15-17 )

ALERT For Mountain Valley Frost Formation Sunday Night Into Monday Morning – Especially For Locations Along & North to Northeast Of The High Knob Massif

Below freezing temperatures will occur at highest elevations into Sunday Morning, amid unseasonably cold wind chills, with limited frost potential across middle to lower elevations where skies stay cloudy.  If skies clear overnight the threat for frost will increase within mountain valleys into Sunday Morning.

Partly to mostly clear skies, low dewpoints, and light winds will promote more favorable conditions for frost formation in valleys during Sunday Night into Monday Morning.  Min temperatures in the upper 20s to middle 30s are expected, with coldest conditions within mid-upper elevation valleys in the High Knob Massif to Burkes Garden corridor of southwestern Virginia.

Widespread frost will be possible on valley floors and impact communities such as Addington, Big Laurel, Burkes Garden, Coeburn, Dante, Elk Garden, Georges Fork, Nora, Norton, Ramsey, Stephens, Tacoma, Tazewell and Trammel ( to note only a few ).  Shady Valley and other typically cold valleys in NE Tennessee and NW North Carolina will also be at risk.

Little to no frost is currently expected on exposed middle elevation mountain ridges & plateaus, and within major river valleys where fog formation will be likely along rivers such as the Clinch, Powell, Holston, Cumberland, and in lower portions of the Russell Fork and Levisa Fork drainages.

Overnight Into Sunday Morning

Partly to mostly cloudy.  Cold.  Gusty WNW-NW winds 5-15 mph, with higher gusts, along mountain ridges below 2700 feet ( decreasing some into morning ).  NW-N winds 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures dropping the 30s, except 20s to around 30 degrees in colder locations at the highest elevations.  Wind chills in the 20s along upper elevation mountain ridges ( 10s in gusts on the highest peaks ).

Sunday Afternoon

Mostly sunny.  Deep blue skies.  Unseasonably cool.  Winds WNW at 5-15 mph, with higher gusts.  Temps varying from the 40s in upper elevations to the upper 50s to low-mid 60s.

Sunday Night Into Monday Morning

Mostly clear evening skies with some increasing high clouds overnight into morning.  W-NW evening winds shifting N to NE into morning at under 10 mph.  Temperatures varying from 30s to lower 40s on mid-upper elevation mountain ridges-plateaus to the 20s to lower 30s in colder valleys with patcy to widespread frost formation.  Fog possible within major river valleys and around large lakes.

Monday Afternoon

Increasing clouds.  Milder.  ESE-SSE winds at generally less than 10 mph.  Temperatures varying from 50s across upper elevations to the 60s in lower-middle elevations.

Monday Night Into Tuesday Morning

Showers developing.  Thunder possible.  SSE-SSW winds increasing to 5-15 mph, with higher gusts, along middle elevation mountain ridges-plateaus.  SSW to SW winds at 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures in the 40s to lower-middle 50s.

Tuesday Afternoon

Showers & thunderstorms becoming likely.  Locally heavy rainfall.  SSW-SW winds 5-15 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  SW-WSW winds 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures in the 50s to lower-middle 60s.

 

Weather Discussion ( May 14-17 )

A gusty and colder air mass moved into the mountains during Saturday with falling afternoon temperatures felt along and north of the High Knob Massif.

Saturday afternoon ( May 14 ) temperatures fell through the 50s into the 40s amid middle elevations along and north of the High Knob Massif ( locations between 2000 & 3000 feet ).  This included Norton, Wise, and adjacent communities.

Locations above 3000 feet, amid the upper elevations, saw temps drop through the 40s into the 30s.

Temperatures dropped into the 30s between 4:00 to 5:00 PM atop the High Knob Massif and Black Mountain, with much colder wind chills on gusty NW winds.

Breaks in the overcast occurred lee of the Cumberland Mountains and adjacent Cumberland Plateau, with some low-level terrain blocking also slowing down the cold air advection.

The result was large temperature differences between locations along and north-northwest of the High Knob Massif verses places to the south and southeast ( 30s and 40s verses 50s and 60s ).

Focus on Saturday Night into early hours of the overnight were on partly-mostly cloudy skies and temperatures that had already dropped below freezing at highest elevations.

At 2:15 AM a air temperature of 30 degrees combined with N wind gusts to 20 mph to generate a 17 degree wind chill factor at the 4031 foot elevation of the Black Mountain Mesonet site located along the Virginia-Kentucky border ( near Harlan-Wise line ).

Forecast soundings above Wise show that the air dries significantly into Sunday with deep blue skies like autumn  ruling the mountain landscape through the afternoon.

Although an increase in high altitude cloudiness is shown into Monday morning ( below ), the low-level air remains very dry with dewpoints in the 20s amid middle to upper elevations being conducive for strong radiational cooling and development of cold air drainage flows into mountain valleys during Sunday Night.

The threat for widespread frost must be respected, especially in mountain valleys of Wise, Dickenson, Russell and Tazewll counties where air will be driest at 900-800 mb. A freeze being possible in colder locations.

Little to no frost is expected on exposed middle elevation mountain ridges & plateaus, and within major river valleys where fog formation will be possible along rivers such as the Clinch, Powell, Holston, Cumberland, and in lower portions of the Russell Fork & Levisa Fork drainages.

Focus into the new work week shifts back to wetness, with showers and downpours in thunderstorms expected to return by Monday Night into Tuesday.

May 2016 has already produced as much or more rainfall than March+April combined in many places along the mountainous Virginia-Kentucky border.