Mountain Area Forecast ( Nov 19-21 )

***A NO BURN BAN REMAINS IN EFFECT

A sharp temperature drop will occur between the predawn to sunset period of Saturday, with falling temperatures combining with gusty WNW winds to generate bone-chilling conditions.  Flurries and snow showers will be likely Saturday Night into Sunday AM, with a dusting up to 1″ possible along the upslope side of the mountains ( with riming at highest elevations ). 

Caution advised for those hunting and/or outdoors this weekend given this is the first wintry blast of the season ( it will feel very cold ).  A few slick places, or even sections, could develop on roads ( especially in favored upslope locations at higher elevations )  Saturday Night into Sunday Morning. 

Relative humidity will remain moderate-high along the upslope side of the mountains during the weekend, before sharp drops in values occur into early next week ( especially in upper elevations ).

Overnight 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 changing to snow showers in the mid-upper elevations.  Windy.  W-NW winds 10-25 mph, with higher gusts.  Temperatures falling into the 30s 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 single digits possible on highest peaks above 3500 feet by afternoon ).

Saturday Night Into Sunday Morning

Chance of flurries & snow showers along the upslope side of the mountains.  Cold & windy.  WNW to NW winds at 10-25 mph, with higher gusts.  Temperatures dropping into the middle 10s to mid 20s ( coldest at the highest elevations ).  Wind chills varying from -5 below to 5 above zero at highest elevations, in gusts, to the 10s in lower-middle elevations.

Sunday Afternoon

 Becoming partly-mostly sunny.  Cold.  WNW-NW winds 10-20 mph, with higher gusts.  Temperatures varying from the low-mid 20s in upper elevations to the low-mid 30s ( milder south into the Great Valley ).

Sunday Night Into Monday Morning

Clear & cold.  WNW-NW winds 5-15 mph, with higher gusts, along middle elevation ridges and plateaus below 2700 feet.  Winds NW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures in the 10s to mid 20s, near steady or slowly rising overnight at highest elevations.

 

Weather Discussion ( Cold Blast )

Saturday Afternoon Update

Official precipitation totals up to around 4:00 PM included 0.22″ on the campus of the University Of Virginia’s College At Wise and 0.30″ at the City of Norton Water Plant.

Snow flurries and occasional pellets of sleet fell in Norton-Wise all afternoon.  Trees at the summit of High Knob had a light, visible coat of rime as late afternoon clouds lifted just enough to see the crest lines.

Saturday Morning Update

I have updated my forecast to take out the likely wording and to just have a change to snow showers in mid-upper elevations  ( this may also include some lower elevations along-north of the High Knob Massif-TN Valley Divide ).

Some flakes are already falling in Wise and a little is actually beginning to stick at the summit level of the High Knob Massif where temps have dropped into the 20s as of 10:00 to 10:30 AM.  Wind chills are already running as low as 10 to 15 degrees up top.

This cold followed around 0.30″ of rain at the summit level.

This cold blast means business, even though total accumulations will be limited across the area.  Reference my previous discussion.

 

Previous Update

The first true blast of winter conditions will make even the most hardy shiver by later Saturday into Sunday morning.

This will be especially true since even highest elevations climbed into the 60s during Friday afternoon.

Wind speeds are increasing across higher elevations within the Cumberland Mountains as a large vertical temperature spread ( 20 to 30 degrees ) has now formed between colder valleys ( in the 30s ) versus milder, increasingly windy ridges ( in the 50s & 60s ) as I had forecast.

*These temperature differences will tend to narrow into morning as vertical mixing increases and causes locally dramatic valley temperature jumps as high ridges ( which are holding steady ) begin to tumble by around sunrise.

Reference my 111816 Forecast for details.

While this will not be the significant precipitation event hoped for, it will be beneficial in terms of adding some wetness and increasing RH values.  This will be especially true along the upslope side of the mountains where rain showers, snow showers, low cloud bases and riming ( at highest elevations ) on WNW-NW flow will combine.

Low-level moisture, in lowest levels of the atmosphere, will be limited with only extreme northern portions of West Virginia, northeastward along the Appalachians, receiving Great Lake moisture advection ( transport ) near the surface.

Due to friction within the planetary boundary layer ( PBL ), the flow turns across the surface isobars as roughly depicted by wind streamlines ( above & below graphics ) such that transport of moisture will be more west to west-northwest downstream of the Great Lakes.  This causes the southern Appalachians to miss out, with flow from mid-continent, on this moisture.

Going above the surface layer, into the 950 to 850 MB zone, there will be some flow across the Great Lakes that reaches into the southern Appalachians ( especially for locations northeast of the Smokies from Lake Michigan ).

 Given very cold air and strong forcing ( torque forces ) this should be enough to at least generate the first widespread flurries and snow showers of the season, with a dusting up to around 1″ of accumulation ( perhaps locally more ) being possible along the windward side of the mountain chain, especially amid favored locations such as the High Knob Massif, Mount Rogers-Whitetop, Roan Mountain, and the Brumley-Beartowns of Clinch Mountain ( to note a few ).

The Bottom Line…A very cold weekend is upcoming with big stories being how COLD it will feel, the first widespread flakes, and the continued lack of a needed significant precipitation event.  This is; however, part of a changing pattern that will feature more chances for precipitation in days and weeks ahead.  Drought does not strike all at once, so in most cases it takes time to reduce and end its impact ( southwestern VA being amid a short-term drought versus locations to the south where much of 2016 has been dry ).