Reference Mid-Winter 2021_High Knob Massif for a recap of recent conditions, as well as a 2020 precipitation update.

Monday Evening Update: 11:00 PM (1 February 2021)

Roadways at all elevations are either snow covered or are becoming snow covered across all upslope locations within Dickenson & Wise counties.

Please use extreme caution into Tuesday.

Event snowfall totals as of 10:44 PM varied from 2.5″ in Clintwood to 11.0″ on Eagle Knob of High Knob Massif, where wind blown snow was becoming more of a factor (snow depths increased between 1″ and 4″ in the above scene during the past 4 hours).

Thanks to my friend Cody Blankenbecler, as always, for these Eagle Knob reports.

Updated at 10:00 PM on 31 January 2021

ALERT For A Prolonged NW Flow Snow Event From Monday Morning Through Wednesday AM (1-3 February 2021)

Snowfall Forecast
(Total For 1-3 February)

4″ to 8″ below 3000 feet

8″ to 12″+ above 3000 feet

4″ or less in downslope areas

Target Snowfall 8″ at 3000 feet: (+/-) 2″ Error Potential,
implying a potential for 6″ to 10″ of snow at 3000 feet in
the 3-day period during 1-3 February 2021.

Significant rime formation is also expected at upper elevations, potentially enough to droop or even break tree limbs and small trees.

Total ground depth is expected to generally be less than total snowfall due to low density snow and significant settlement over time, in combination with some melting and sublimation. The exception will be at upper elevations where areas of blowing snow and drifting are likely to cause greatly varied depths and much deeper snow in drift zones.

Residents and those traveling at high elevations should plan for the possibility of impassible roads, especially in windward facing basins and mountain ridges from Big Cherry Lake to High Knob Lake, and locally in other places within the high country above 3000-3500 feet.

Deep moisture and seasonally cold air aloft will combine to generate widespread snow during Monday into Tuesday morning. Snowfall from Tuesday AM through Wednesday AM will become more showery, and due to more shallow moisture, more restricted to windward slopes of the major orographic zones.

While forecast models and forecasters say that this event will last until Tuesday morning, the model streamline flow field trajectories predict it will persist into Wednesday morning for the orographic upslope locations along-northwest of the major mountain barriers, especially the Cumberland-Allegheny Front where shallow moisture being lifted will be most productive as actual, documented past observations illustrate.

Relationship Between NW Flow Snowfall And Topography

It would be a better forecast world if forecasters would seriously look at research already done by Baker Perry, Charles Konrad, and even myself (locally in southwestern Virginia) with respect to snowfall and topography and stop following this model bias toward the Blue Ridge given elevation is only a single factor within a complex array of factors that determine snowfall.

Although models have gotten better at showing general terrain distribution (now showing a “horseshoe” configuration around the TRI), they still often over-estimate snowfall in locations that are colored dark-grey in the above graphic from Baker Perry & Charles Konrad.

Past climatology of these flow events shows that highest total snowfall amounts tend to occur from the High Knob Massif to Snowshoe Mountain and Canaan Mountain along the Cumberland-Allegheny Front, with a secondary maximum (often less, but not always) along the Blue Ridge (which are the primary, or initial, lifters on SE flow trajectories).

This is opposed to forecast models and forecasters who persistently focus upon the Eastern Continental Divide, which is the secondary lifting zone in NW flow settings (the Great Smokies, being farthest southwest, function more as the primary lifting zone at their latitude given the lower terrain to their northwest. The main hinderance on NW Flow for the Smokies being Great Lake moisture advection is often not as abundant at their latitude versus farther northeast along the Appalachians, with abundance increasing from southwest to northeast along the mountain chain with respect to Great Lake moisture in the mean).

Every snowfall event is different, and in this case streamline predictions are for Great Lake moisture transport far to the south. I have no problem with heavy snowfall amounts being predicted for the Great Smokies. The problem, is that Winter Storm Warning snow within this type of setting is a no-brainer from the High Knob Massif to Canaan Mountain.

Highest snowfall amounts will occur along the windward mountain barriers, along and west to northwest of the Cumberland-Allegheny Front as well as along and adjacent to the Eastern Continental Divide.

Part 1: Miller B Winter Storm

With the above duly noted, no Winter Weather Advisory or Winter Storm Warning was issued for Wise County for Part 1 of this event (despite 1.5-2.5″ or locally more in Norton-Wise-Sandy Ridge, as well as Black Mountain, and 6-7″ above 3000 feet in the High Knob Massif).

If there is nausea about including the Powell River Valley, then begin breaking out northern Scott and highest elevations of Lee to go with mid-upper elevations in Wise County as a separate forecast zone from the Powell & Clinch river valleys that could form a separate (lower elevation) forecast zone.

Nothing. Nada, to follow a trend that is reverting back to pre-2008 when the MRX NWSFO would persistently group Wise County with Great Valley counties.

Nearly all precipitation fell as snow at upper elevations of the High Knob Massif into morning hours of 31 January, with 6″ to 7″ of snow accumulating from the Little Mountain community adjacent to Big Cherry Lake to the High Chaparral, Robinson Knob, and Moore Knob communities.

Locally greater amounts may have occurred at highest elevations, but due to severe winds and significant blowing snow-drifting it was nearly impossible to determine.

Extreme Winter Potential

The potential for extreme winter conditions is being monitored for late this weekend into next week.

While model timing and intensity vary, both the European and GFS are currently predicting that bitterly cold air will move across the North Pole and plunge southward through Canada into the USA by next week.

The coldest mass of air in the Northern Hemisphere, relative to climatological means, is being predicted to plunge into the central-eastern United States.

This is an end result of a Major Sudden Stratospheric Warming event observed during January, as have been (which can be debated if wished) the recent, current and future snowstorms impacting the region.

Review the Sudden Stratospheric Warming video by the MET Office in this section to aid understanding of how a major SSW event can trigger an arctic outbreak.

Although it remains too early to know if this will verify, there is increasing confidence in an arctic outbreak impacting portions of the United States by next week.

Stay tuned for later updates.

Previous Discussion

ALERT For A Period Of Accumulating Snow And/or Sleet-Rain Around And Following Sunset Saturday Evening (30 Jan 2021)

While virga (snow aloft) was developing above the area early Saturday afternoon, nothing more than flurries or sleet pellets will reach the surface until later this afternoon-early evening due to dry, low-level air.

A more organized band of precipitation, mainly snow or snow-sleet, will develop by around and after sunset this evening along a warm front.

Snow-Frozen Type Forecast
Part I of A Three Act Storm

Saturday Night to Sunday Morning

Accumulations are expected to vary from a dusting toward the Virginia-Tennessee border, to the southwest of the High Knob Massif, up to 3″ at highest elevations and toward the northeast of the High Knob Massif-Tennessee Valley Divide.

Locally greater amounts, more than 3″, could occur at highest elevations in the High Knob Massif if part of the next wave coming in during early hours of Sunday is snow or snow-sleet prior to changing to freezing rain-rain on strong upslope flow across cloud-engulfed upper elevations.

Although temperatures above the summit-level of the High Knob Massif will rise above freezing into Sunday, adiabatic cooling on strong upslope flow over snow cover will maintain a much colder temperature profile at ground level. This will cause the bulk of precipitation to fall in frozen form at highest elevations in the High Knob Massif, with initial snow changing to sleet and freezing rain (and just rain eventually, as upslope weakens and the flow direction shifts).

Dusting Up To 3″

A complex Miller B Winter Storm will impact the mountain region this weekend through early next week, with three distinct phases (parts).

Part 1 = Initial snow-sleet-freezing rain along a warm front (Saturday evening)

Part 2 = Transition to rain Sunday (potential for freezing rain at highest elevations in the High Knob Massif)

Part 3 = Prolonged period of NW-N Upslope Flow Snow from late Sunday Night into Tuesday afternoon or night

Significant snow accumulations along the upslope side of the mountains are expected with Part 3. My preliminary estimate, which will likely change, is 4″ to 8″+ for locations along and northwest-north-northeast of the High Knob Massif and Cumberland Front.

Secondary zones with enhanced snowfall will occur along the Brumley Mountain to Burkes Garden section of Clinch Mountain, and from the Mount Rogers-Pine Mountain area southwest along the Tennessee-North Carolina border to include Mount Mitchell.