ALERT For Icy Walks-Decks-Above Ground Objects And Roadways Overnight Into Early Afternoon Wednesday
Drizzle & Fog Changing To Freezing Drizzle & Freezing Fog With Especially Dense Fog Amid Upslope Locations Along & North of the High Knob Massif and Tennessee Valley Divide Overnight Into Wednesday
Area Of Greatest Freezing Fog Impact Covers Hundreds Of Square Miles
This setting favors very dense fog for Wise and places of similar or higher elevation along and north of the High Knob Massif and the Tennessee Valley Divide overnight into Wednesday. Please slow down and use extreme caution walking outside and/or driving.
Overnight Into Wednesday Morning
Turning colder ( inversion developing ). Freezing drizzle and freezing fog – worst at mid-upper elevations. NW-N winds 5-15 mph. Temperatures falling into the 20s, with upper 10s at highest elevations by morning. Wind chills falling into 10s to low 20s overnight into morning, with single digits & 10s at highest elevations ( milder temps in river valleys of Clinch, Powell, Holston toward Tri-Cities ).
This Morning Through This Afternoon
Cloud bases lifting and becoming partly sunny. Light N to NE winds generally less than 10 mph, becoming variable. Temperatures mostly in the 20s to mid 30s ( milder south toward the Tri-Cities and river valleys of Clinch & Powell ).
Tonight Into Thursday Morning
Becoming clear. Areas of fog possible. Winds becoming SSW-WSW at 5-15 mph along mid-upper elevation ridges, with higher gusts by morning. Temperatures varying from the 10s to low 20s in colder locations verses rising readings on exposed mountain ridges above 2700 feet.
Weather Discussion ( January 26-27 )
Afternoon Update
Cloud bases began lifting off of middle elevations this morning, with breaks for sunshine developing into early afternoon ( northern slopes of the High Knob Massif and portions of the Tennessee Valley Divide being slower to break for sun than locations lee of the mountains into portions of the Clinch River Valley ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
While some clouds still linger along northern sides of the High Knob Massif, the view is certainly better than 12-hours earlier when the area was engulfed amid freezing fog.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Temperatures are slowly beginning to rise with upper 20s to lower 30s from Norton-Wise to Clintwood at 2:00 PM, in wake of low temps which occurred at mid-morning.
Nora 4 SSE Observations at 2650 feet Elevation
A feature of note this afternoon is a nice, stationary orographic wave cloud which has now held in the same position for a couple hours or more.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Other waves are visible, but this orographic cloud has tended to be the biggest and most predominate seen from this CAM perspective.
Observe also miles of riming visible along the High Knob Massif from the prolonged freezing fog event of Tuesday Night into today.
High Knob Massif Webcam
It changes shape a little and color as light changes, but basically holds in the same place over time. It is present in the first image above at 2:18 PM and remains in this latest image at 4:14 PM.
NASA Visible Image At 3:00 PM on Wednesday – January 27, 2016
Looking downward from space ( above ) three such clouds are visible along the Wise-Scott border of the High Knob Massif, with the middle one being the cloud best seen in above CAM images.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Mountain waves ( above ) after sunset with more defined stacked lenticular forms in the same location as the long-lived afternoon wave that possessed more of a roll-type appearance. Very nice!
High Knob Massif Webcam – University Of Virginia’s College At Wise
Observe the “white light” above Eagle Knob which is the PBS Transmitter Tower at 4413 feet above sea level ( appears red to naked eye, as this is the infrared night mode of the High Knob Massif Webcam ).
My Overnight Discussion
A raw and nasty Tuesday was dominated by rain, gusty winds at higher elevations, and a general array of fog that formed over the cold snowpack as moist, milder air was transported across the area on southerly air flow.
High Knob Massif Webcam – University Of Virginia’s College At Wise
That played a major role in my forecast last night, in which I greatly undercut model forecast temperatures for Tuesday ( reference my 012616 Forecast for more details ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
Now my ALERT for Freezing Drizzle & Freezing Fog should be taken seriously by everyone planning on being outside overnight into Wednesday. Be careful walking-driving as any surface could be icy & slick.
The Norton-Wise temp being 30-32 degrees at 11:30 PM.
Lonesome Pine Airport In Wise
The setting from now through the overnight is all about cloud bases which are dropping on northerly upslope flow and temperatures that go sub-freezing to generate an array of icy conditions on above ground and ground surfaces.
Temperatures at 11:30 PM on January 26 included
Black Mountain: 28 degrees ( Elevation 4031 feet )
Lonesome Pine Airport: 32 degrees ( Elevation 2684 feet )
While the entire area will be dropping below freezing into Wednesday morning, locations from Norton-Wise & Sandy Ridge are at or below freezing now and will fall into and through the 20s into the upcoming day ( reaching a MIN around mid-morning Wednesday, followed by steady or slow rises through the afternoon with small recoveries ).
NAM Model Forecast Sounding Above Wise at 7 AM Wednesday ( Jan 27 )
The moisture profile appears to become too shallow to support any snow, with freezing fog and freezing drizzle being favored instead amid upslope locations along and north of the High Knob Massif and Tennessee Valley Divide ( given this thermal structure ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
The biggest unknown during this forecast cycle arises by late today when high-resolution models like the NAM show a shift in wind directions working downward from top of the inversion layer ( above High Knob summit level in the morning to below its level by late afternoon ). Depending upon when this occurs, cloud bases will begin to lift and break up ( it may be during mid-late PM or after sunset ).
Climatology shows it could be BOTH. Settings like this in the past have featured clearing across the high country of the High Knob Massif before it occurs from Wise northward to Pound-Clintwood as moisture thins from top to bottom. Snow on the ground acts as a complicating factor; however, since it keeps low-levels cold and can enhance a vertical inversion ( warmer air over cold air ). If the snow effect is strong enough then clouds may just hold right into Wednesday evening.
Regardless of how this plays out exactly, it will be another raw day and I have again undercut temperatures to make them colder than guidance suggests as many places along and north of the High Knob Massif and Tennessee Valley Divide will remain below freezing all day. Keep warm!
