My Forecast For Today ( February 10 )
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.
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 ).
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.
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 ).
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
February 9 at 4:00 AM
February 9 at 9:00 AM
February 9 at 3:00 PM
February 9 at 9:00 PM
February 10 at 3:30 AM
February 10 at 9:00 AM
February 10 at 3:00 PM
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.
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.