ALERT Continues For Icing With Freezing Rain At High Elevations In The High Knob Massif – Mixed With Snow – With An Ice Storm In Progress
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Significant Ice Storm In Progress – Eagle Knob of High Knob Massif – 7:40 PM March 24
*A notable increase in ice accumulation is occurring.
An all out ice storm is in progress in the high country with the potential that the freezing level will drop as 925-875 MB winds back more E-ENE during the evening to also impact communities near and above the level of Flat Gap.
Trees & power lines have started to droop under increasing weight of ice forming at upper elevations in the High Knob Massif, with worst icing above 3300 feet ( note ice & icicles on chain link fence on Eagle Knob ). Snow continues to be mixed during periods of heavier precip ( bright banding on Doppler often indicates this ).
Travel along State Route 619 and Routes 237, 238 and others at the upper elevations is discouraged. Travel along Route 237 has been nearly impossible and restricted to high profile 4×4 vehicles.
At middle to lower elevations along and north of the High Knob Massif temperatures are marginal in colder locations, with 32.7 degrees officially in Clintwood as of 8:00 PM.
ALERT For Areas Of Very Dense FOG Through Saturday Evening Into Early Hours Of Sunday ( March 25 )
High Knob Massif Webcam – University Of Virginia’s College At Wise
Although clouds ( dense fog ) have been widespread at upper elevations throughout Saturday, an increasing concern through Saturday Night will be reduced visibility within areas of very dense fog at middle-lower elevations. Locations with snow cover will have some of the worst fog.
ALERT For A Slower Than Expected Change From Snow To Rain In Wise & Dickenson Counites – Power Outage Potential Increasing
As of early Saturday PM a general 3″ to 5″ of wet snow had accumulated across much of Wise and Dickenson counties, with a slower than expected change. Despite temperatures within the lower 30s snowfall has been heavy enough to accumulate. Mixed sleet has also occurred. Should this continue it will greatly increase risk of power outages.
*Due to sinking air off the High Knob high country on SE flow the amount of snow drastically decreases to the southwest toward Powell Valley and Big Stone Gap.
The atmosphere has become nearly isothermal through a deep layer. It is hoped that afternoon rises will help deter this increasing threat and that these counties will not have to be added into the region facing a crippling fall of snow.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The Heaviest Precipitation Is Yet To Come Into Late Saturday and Saturday Evening and the form it takes will determine how critical this situation becomes. A change to rain is still being predicted by models even though it has been very slow to occur.
ALERT For The Potential Of A Crippling Fall Of Wet Snow Across Eastern Portions Of Southwest Virginia Within A Corridor Between Marion And Martinsville, Centered Upon The Greenbrier And New River Basins
Travel into eastern portions of southwestern Virginia is expected to become hazardous during Saturday, with the potential for a crippling fall of wet snow. Travelers who plan on attending the NASCAR races in Martinsville should be aware that travel along I-81 and Route 58 could become impossible during the climax of this event.
Overnight Into Friday Morning
Partly-mostly clear. Cold. WNW-NW winds 5-15 mph with some higher gusts along middle-upper elevation mountain ridges. Temperatures dropping into the 20s, with 10s to low 20s in coldest upper elevations sites. Wind chill factors in the 10s & 20s, except single digits along highest mountain ridges at upper elevations.
Friday Afternoon
Mostly sunny, with increasing high clouds by mid-late afternoon. Seasonally cold. NW winds 5-15 mph, with higher gusts. Temperatures varying from 30s at upper elevations to the mid 40s to lower 50s.
Friday Night Into Saturday Morning
Increasing clouds. Snow developing during the predawn hours, possibly beginning as a mix or rain, especially to the southwest and south of the High Knob Massif. Variable winds generally less than 10 mph. Temperatures falling into the upper 20s to lower 30s.
Saturday Morning Through The Afternoon
Morning snow or mixed precipitation giving way to rain. Rain may be heavy at times. Cold & nasty. Freezing rain with significant icing possible in the High Knob Massif. Winds SE-SSE at 5-15 mph, with higher gusts, at elevations below 2700 feet. SSE-SSW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures hovering into the 30s to around 40 degrees ( 30-33 degrees in the High Knob Massif ). Areas of dense fog, widespread at the upper elevations.
Saturday Night Into Sunday Morning
Evening rain giving way to overnight showers-drizzle. Freezing rain at upper elevations in the High Knob Massif with a chance of freezing rain at colder mid-low elevation sites. SE-SSE winds shifting ESE-ENE at 5-15 mph with higher gusts. Temps in the 30s. Areas of dense fog.
A setting favorable for heavy to excessive precipitation continues to be monitored for next week. Please stay tuned for later updates on a stormy pattern to close March 2018.
Weather Discussion ( Nasty Pattern )
Saturday Afternoon Update
What is arguably the most sloppy ( NASTY ) system of the entire 2017-18 Winter Season has produced essentially all precipitation types across the mountain area today, with a significant amount of snow and icing.
GOES-16 Mid-level Water Vapor Image At 6:30 PM on March 24, 2018
850 MB Streamlines Showing Air Mass Clash ( March 24 )
A clash between air masses with mT ( maritime-tropical ) and cP ( continental polar ) characteristics is creating havoc across the region today as seen on current GOES-16 images.
A looming and potentially MAJOR weather maker is also already clearly visible on this image, a large river of atmospheric moisture streaming across the Pacific Ocean into the western-southern USA. This will set the stage for what could be a heavy to excessive precipitation event next week.
250 MB Jet Stream Flow Across Pacific Into USA
Given significant snow depths-water content at upper elevations now, and observed water flow during Friday, this needs to melt and flush out of drainage basins of the Clinch, Powell, and adjacent Cumberland before any such system develops.
Late Friday Evening Update
Snow Drifts Along High Crest Lines In High Knob Massif – Friday PM of March 23
Portions of Route 237 ( between High Knob and Big Cherry Lake ) continued to be covered by snow-ice late on Friday, March 23, with large snow drifts remaining along high crest lines.
A significant weather event is expected to develop across southwestern Virginia during Saturday, with a nasty array of weather conditions.
While temperatures aloft will dictate major precipitation types, low-level temperatures will also be locally critical.
Black Mountain Mesonet At 12:05 AM on March 24, 2018
Adiabatic upslope cooling into the high country along the Wise-Scott-Lee County border may require an ICE Storm Warning ( the Wise-Harlan County border may also be impacted, but with less severe conditions ).
Following morning snow or mixed precipitation most of the area is currently expected to change over to a cold rain, but temperatures will remain unseasonably cold and it could be a close call for many locations. Stay tuned for updates that may be needed as this system develops.
Previous Discussion
Sunshine during a TGIF should be savored as a truly nasty setting develops into this weekend as another significant precipitation event unfolds.
High Knob Massif Webcam – University Of Virginia’s College At Wise
March 22 began with stacked lenticular clouds above the rime capped crest zone of the High Knob Massif.
Snowfall Totals & Ground Depths ( As of Morning of March 22 )
City of Norton Water Plant: 3.0″ 2″ ground depth ( 1.28″ event total )
High Chaparral: 3.5″ ( 2-3″ ground depth )
High Knob-Eagle Knob: 7.0″ ( Variable depths with 1-2+ feet drifts )
This event continued to accentuate the wetness of 2018 with more than 2.00″ of total water equivalent precipitation falling during the March 16-22 period at Big Cherry Lake Dam ( 4.86″+ in March and 24.71″+ since January 1 ).
Snowfall and snow depths generally came in on the lower end of my forecast spread with this most recent event. The exception being at upper elevations in the High Knob Massif between Bowman Mountain and the Thunderstruck Knob of Powell Mountain, where up to 7″ or more of snow fell.
GOES-16 Visible Image At 10:17 AM on March 22, 2018
Although a mixture of clouds and snow were present, there was no mistaking the outline of the High Knob Massif as it stood above the horizon of far southwestern Virginia on morning GOES-16 satellite imagery ( above ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A thin layer of orographic clouds were forming along the summit of the massif at the time of the GOES-16 image, as viewed from the UVA-Wise Webcam above, and with motion were observed to be part of standing waves through which the air passed as it flowed southeastward toward the TRI.
NAM 12 KM Model Total Precipitation Forecast – Next 84 Hours
The main focus now shifts to the next system which will be a wet one, with generally good model agreement on a well defined corridor of moisture; although, total amounts of precipitation remained varied.
GFS Model Total Precipitation Forecast – Next 84 Hours
Thursday evening ( 00 UTC ) runs of both the NAM and GFS models shifted more toward the ensembles of the GFS and European Model with respect to placement of the main axis of this precipitation corridor.
NAM 3 KM Model Total Snowfall Forecast – Next 60 Hours
Models remain in considerable disagreement as to how much cold air deep enough to support snow will remain in place; therefore, they diverge on potential amounts.
GFS Model Total Snowfall Forecast – Next 60 Hours
The axis of the snowband is similar on both models during this run, but amounts for locations outside the axis varies.
At the Wise gridpoint, for example, model forecast snow amounts range from 1″ on the high-resolution NAM 3 KM Model to 5″ on the GFS Model ( the 12z run of the European Model was a compromise with 3″ predicted ).
If the precipitation band shifts southwest or northeast these amounts will change, and potentially in a big way.
Past climatology with warm fronts suggests that the area to the north and east of the Cumberland Mountains, focused upon the New River and Greenbrier valleys, will be most favored for a significant amount of wet snow. That is the model consensus.
If movement of the actual low center ( the storm track ) shifts more south, then that would keep this area within snowfall for a longer period of time versus if the the storm track shifts north. There remains some wiggle room.
