ALERT For Bitterly Cold Temperatures-Wind Chills Today Into Thursday AM. This Pattern Will Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.
Please Remain Alert For Hazardous Traveling Conditions As Well As Ice On Decks-Porches-Walks.
Some additional light snow accumulations will be possible through today, with locally heavier amounts along windward slopes of the High Knob Massif & Black Mountain. Much of the middle-upper elevations will again remain in 10s & single digits through today ( coldest conditions at the highest elevations ).
Potential for additional heavy snow is being monitored for the Friday-Saturday period with a Clipper System leading a Major Arctic Outbreak ( with Great Lake connected NW Upslope Flow Snowfall following the upper air disturbance & Arctic Front ).
Bitterly cold conditions are expected by Saturday into Sunday as part of the Polar Vortex gets stretched southward into the Great Lakes and NE USA.
Potential for a Major Winter Storm is being monitored for the period from late in this weekend into early next week.
Overnight Into Wednesday Morning
Light snow & snow showers. Local bursts of heavier snow. Bitter cold. Winds W to NW at 5-15 mph, with higher gusts along mid to upper elevation mountain ridges & plateaus. Blowing and drifting snow with riming at high elevations. Temps from single digits at highest elevations to 10s in Norton-Wise ( milder in lower elevations toward the Tri-Cities ). Wind chill factors in single digits above & below zero, except wind chills as low as -10 to -15 below zero at highest elevations.
This Afternoon
Mostly cloudy ( some hazy sunshine possible ) with a continued chance for light snow, flurries, and heavier local snow showers. Bitter cold. W to NW winds 10-20 mph with higher gusts. Blowing snow on exposed mid-upper ridges. Temperatures varying from the single digits at highest elevations to the mid 10s-low 20s, mildest at low elevations in the Clinch, Powell, Holston river valleys toward the Tri-Cities. Wind chills in the single digits above and below zero, except -5 to -15 below along upper elevation ridges.
Tonight Into Thursday Morning
Mostly cloudy & bitter. Chance of flurries & snow showers. Winds W-WNW 5-15 mph, with higher gusts, along middle elevation ridges & plateaus below 2700 feet. WNW winds 10-20 mph, with higher gusts, on upper elevation ridges. Temperatures varying from 0 to 5 degrees at the highest elevations to lower 10s. Wind chill factors varying from single digits to as cold as -10 to -20 below zero on upper elevation ridges.
Weather Discussion ( February 9-10 )
My Afternoon Update
The only update to my forecast for this afternoon was to increase wind speeds a little, and add blowing snow for the higher mountain ridges ( especially in upper elevations of the High Knob Massif where snow is deep ).
Snow & Blowing Snow – Eagle Knob of High Knob Massif – 2:45 PM February 10
At 2:45 PM the air temperature was 6 degrees on Eagle Knob with wind chill factors as low as -15 degrees below zero. The snowfall total had reached around 18.0″ at 3 PM with large variations in ground depths due to blowing-drifting and settlement.
Joe & Darlene Fields measured 2.5″ of new snow up to 9 AM Wednesday to bring the storm snowfall total to 12.7″ in the High Chaparral community of the High Knob Massif. More snow has fallen & accumulated since that time.
Deep Fluff In High Chaparral of High Knob Massif – 8:50 AM February 10
Joe & Darlene Fields measured 0.5″ more at 4:00 PM to bring their storm snowfall total to 13.2″ in High Chaparral. The mean snow depth was 8″ with a southern exposure there.
*They also lost 1″ of snow depth with melting on February 8 before the colder air and steady snow developed. This illustrates why it is important to measure snowfall using the official method since the combination of many factors work to change ground depths.
If one had only looked at the 8″ depths observed at both the City of Norton Water Plant ( on a north slope ) and in High Chaparral ( south exposure ) it might be assumed that snowfall was the same. However, by measuring the proper way it can be seen that snowfall was greater in High Chaparral than at the Norton Water Plant ( 3.5″ more in High Chaparral ).
There has been more drifting in the High Chaparral area, especially at more exposed sites and in higher elevations where more snow fell from Bowman Mountain to Little Mountain and the head of Big Cherry Lake basin ( but I’m just comparing points for illustration of how mere snow depth alone can be deceptive when not considering the big picture ).
Below is a look at conditions on Stone Mountain Road, up from Tacoma in Wise County ( State Route 706 ), at 1:00 PM this afternoon. It is easy to see why school is closed in Wise County ( remember hundreds of folks live above 3000 feet along the Wise-Scott border area in the High Knob Massif as was well documented by Jessica Swinney in a 2008 study ).
Stone Mountain Road from Tacoma ( State Route 706 ) at 1 PM February 10, 2016
Superintendent Andrew Greear reported 1.4″ of new snow accumulation at the City of Norton Water Plant between 9:00 AM and 3:00 PM today ( Wednesday, February 10 ).
This brings the official storm snowfall total to 9.7″, with around 8″ ( 7-8″ ) currently on the ground at this northern base of the High Knob Massif ( nearly twice this much has fallen at the summit level nearly 2000 vertical feet higher ).
This is a very accurate measurement and has followed the official NWS and University of Colorado Guidelines for measuring snow.
City of Norton Water Plant
February 8 at 10:00 PM 2.2″
February 9 at 4:00 AM 1.9″
February 9 at 9:00 AM 1.5″
February 9 at 3:00 PM 0.7″
February 9 at 9:00 PM 0.5″
February 10 at 3:30 AM 1.0″
February 10 at 9:00 AM 0.5″
February 10 at 3:00 PM 1.4″
Snowfall Total: 9.7″
( 7-8″ of Snow Depth )
*Snowfall measurements courtesy of Scott Craft, Andrew Greear, Caleb Ramsey, Wes Ward, and Joe Carter.
The water equivalent total has been around 0.50″ on nearly 10″ of snow ( 20:1 density ), with the density dropping during the second half of this event at the Norton Water Plant ( i.e., ratio of snow to water has been increasing as the air has turned bitter in Norton ).
This may not be the case atop the High Knob Massif, with only a snow core being able to reveal the results. Past experiences where I have taken cores ( as recently as January 31 ) show that riming of snowflakes adds to the water content along with a tendency when air temperatures get around and below 10 degrees for the density of snow to naturally increase. So the water content on 12-18″ of snowfall up above is likely significantly more than that obtained down in the City of Norton.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The High Knob Massif has been obscured in snow and clouds for days and is only now becoming partially visible along the horizon as moisture finally begins to decrease.
My Overnight Discussion
This active winter pattern is only going to get wilder in coming days, with multiple threats being watched from this current system through the weekend into early next week.
Wes Ward measured an additional 1.0″ of new snow at the City of Norton Water Plant at 3:30 AM to bring the current tally to 7.8″ ( with 6-7″ of settled snow depth ).
City of Norton Water Plant
February 8 at 10:00 PM 2.2″
February 9 at 4:00 AM 1.9″
February 9 at 9:00 AM 1.5″
February 9 at 3:00 PM 0.7″
February 9 at 9:00 PM 0.5″
February 10 at 3:30 AM 1.0″
Snowfall Total: 7.8″
( 7″ of Snow Depth )
*Snowfall measurements courtesy of Scott Craft, Andrew Greear, Caleb Ramsey & Wes Ward.
Reference my 020916 Forecast for details on earlier snow amounts.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Light snow which has never stopped falling along upslope sides of the mountains is picking up a little in intensity, with redevelopment of heavier localized snow showers and snowstreaks ( narrow bands of snow that follow along low to mid-level wind trajectories ), during the late evening-early overnight period.
This has been expected all along as the coldest 850 MB air is still to arrive, along with continuation of 700 MB moisture until early PM. It will not be until mid-late this afternoon that some hazy sun can become more common, and due to very cold air remaining aloft, it could help develop a few heavier snow showers or narrow streaks.
With temperatures now so cold it will not take much snow to make even cleared roads slick, so please slow down and use extreme caution outside through today.
Nora 4 SSE – Official National Weather Service Site In Middle Elevations
I like to use Nora 4 SSE observtions since it is a good calibrated site that is representative of middle elevations across the Norton-Wise & Sandy Ridge areas of Wise & Dickenson counties.
Tuesday temperatures remained in the 10s at most middle elevation sites across Wise & Dickenson counties, with upper single digits to around 10 degrees at the highest elevations in the High Knob Massif & Black Mountain.
Black Mountain MesoNET Up To Midnight – February 10, 2016
Extensive riming has occurred in upper elevations of both the High Knob Massif and Black Mountain, with near saturated air through the afternoon amid bitter temperatures and snow.
A persistent and gusty W-NW wind has made conditions very bitter with chill factors between 0 and -15 degrees below zero along these high mountain crestlines.
Black Mountain MesoNET – Afternoon Wind Graph
This system has possessed abundant mid-level moisture and very cold air aloft that has enhanced instability. Snowfall has been widespread across a wide region and varied in the accumulations due to a number of factors such as the prior warmth-rain of early February, low density snow that tends to settle and/or melt-sublimate faster than wet snow, and a W-NW flow which biases heaviest amounts to windward sides of major mountain barriers like the High Knob Massif.
Once again, this system lacks a Great Lake connected NW flow into the southern Appalachians. Even though windward slopes & crests of the High Knob Massif have again done very well with snowfall, it would have been much heavier had the trajectory crossed the still open expanse of the Great Lakes.
NAM 12 KM Model Backward Airflow Trajectory
An actual Great Lake connected NW Flow might finally develop by late week, along and behind an Arctic Front and upper air wave leading the way for a brutally cold mass of air that will be an actual part of the Polar Vortex that gets temporarily stretched southward in the immediate wake of a major upper stratospheric warming event.
European Model 150 MB Forecast – 7 AM Friday on February 12, 2016
Observe how a piece of the Polar Vortex temporarily breaks away from the main vortex center toward the Great Lakes and NE USA which will be the target of the most brutal air.
European Model 150 MB Forecast – 7 AM Saturday on February 13, 2016
What happens just beyond this time into early next week will be a major concern for the Appalachians, with details still to be worked out by models as arctic air retreats.
