ALERT For Hazardous Road Conditions At High Elevations In The High Knob Massif Into Friday
Eagle Knob of High Knob Massif – March 2, 2018 at 3:03 AM
Roadways at high elevations have become snow covered to partially covered at high elevations in the High Knob Massif with caution advised for travelers along State Route 619, Routes 237, 238, and others at upper elevations.
Reference February 2018 – Wettest On Record In Virginia for a recap of heavy-excessive precipitation and a huge contrast in amounts across the Old Dominion in Meteorological Winter.
Former Alert
ALERT For Strong Rises On Streams Late Wednesday Into Thursday With Flooding Possible – Especially In Low-lying Flood Prone Locations And On Creeks That Drain The High Knob Massif-Black Mountain Area
Rain will develop over the mountains Wednesday, and will become heavy at times, with moderate-strong orographic forcing favoring heavy to locally excessive rain amounts into Thursday ( especially within the High Knob Massif – Tennessee Valley Divide corridor ). Persons living along creeks and in flood prone, poor drainage areas should remain alert for strong water level rises.
Overnight Into Monday Morning
Cloudy & damp with light rain and showers developing, heaviest along-south of the High Knob Massif. Turning cooler. SW winds shifting NW-N at 5-10 mph, with higher gusts. Temperatures dropping into the 30s to lower 40s, coldest at upper elevations.
Monday Afternoon
Becoming mostly sunny by mid-late afternoon. Chilly. Winds N-NE at 5-10 mph with higher gusts. Temperatures varying in the 40s, with 30s at upper elevations. Wind chills around or below freezing on highest peaks.
Monday Night Into Tuesday Morning
Clear & frosty cold. Light winds. Large vertical temp spread developing between colder valleys & milder ridges. Temps varying from the upper 10s to lower 20s in valleys to upper 20s to lower 30s on exposed ridges-plateaus, except locally colder in upper elevation mountain valleys.
Tuesday Afternoon
Mostly sunny ( high clouds developing ). Milder. Winds S-SW at 5-15 mph, with higher gusts. Temperatures varying in the 40s and 50s ( coolest at upper elevations ).
Tuesday Night Into Wednesday Morning
Increasing mid-high clouds. SSE-SSW winds 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. SW-WSW winds 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from 30s in sheltered valleys to the 40s ( a few sheltered valley could drop into the 20s before rising overnight into morning. Wind chills in 30s on upper elevation mountain ridges.
Wednesday Morning Through The Afternoon
Rain developing. Chance of thunder. Rain may be heavy at times. SSE to SSW winds 5-15 mph, with higher gusts, below 2700 feet. Winds SW to WSW 10-25 mph, with higher gusts, above 2700 feet. Temperatures in the 40s to around 50 degrees. Widespread dense fog developing at upper elevations, with areas of fog at other elevations.
Wednesday Night Into Thursday Morning
Rain, heavy at times. Winds becoming SSW-SW at 10-25 mph, with higher gusts. Dense fog at upper elevations, with areas of fog at lower-middle elevations. Temperatures near steady or rising in the 40s to low-mid 50s.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible warnings that may be needed into the overnight-day of March 1.
Windy and much colder conditions with a change from rain to snow is expected by Thursday Night into Friday Morning. Some accumulation will be possible, especially at elevations above 2500-3000 feet.
Weather Discussion ( Record February )
February 27 ( Tuesday PM ) Update
A frosty cold Tuesday greeted the mountain landscape with temperatures varying from 10s amid colder valleys at upper elevations to the 30s on exposed ridges-plateaus.
Freezing fog occurred in many valleys, especially at low-middle elevations, in wake of unseasonable warmth and record wetness.
GOES-16 Mid-level Water Vapor Image
The current GOES-16 global view is NOT a repeat of a couple weeks ago; although, it does appear that way with a notable plume of moisture again streaming toward the region from the tropical Pacific that will join Gulf of Mexico energy.
A 30-50 Knot 850 MB flow must be respected as it streams toward the favored orographic lifting zones, especially on the windward side of the Cumberland Mountains.
Town of Appalachia Lake Water Plant – Data From Superintendent Mark Quillin
February 2018 precipitation totals have now topped a FOOT within the High Knob Massif to Black Mountain corridor, to include valley locations around Appalachia, Big Stone Gap, and locations near the City of Norton.
Black Mountain Mesonet – February 1-26, 2018
So despite what flash flood guidance shows, it will not take nearly as much rainfall as often would be required to cause strong rises on creeks, especially within this very wet area centered over Wise, Harlan, northern Scott, and northern Lee counties.
Previous Discussion
Although the mountain area was lucky and caught a break last week as the Bermuda-like High off the southeast USA coastline remained strong enough to keep persistent rains west of the southern Appalachians, enough has now fallen to make this the wettest February on record in many places.
Black Mountain Mesonet ( February 1-25 )
A general 13.00″ to 14.00″+ of total precipitation has now fallen in upper elevations of the High Knob Massif-Black Mountain area, which is record breaking for at least the state of Virginia during February.
*A total of 8.59″ in Clintwood breaks the previous record of 8.08″ set back in February 2003 ( records date back 54 years to 1964 ).
A general 0.90″ to 1.50″ fell during the weekend, with 1.14″ at the City of Norton Water Plant and 0.94″ in Clintwood.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The next significant rain event will miss morning recording times on February 28, but could contribute more to monthly tallies if running them up to Midnight; however, the Euro is predicting that the heaviest rains will arrive after Midnight on February 28 into the first day of March 2018.
European 51-Member Ensemble Mean 500 MB Height Anomaly Forecast: Days 0-4
A significant pattern change, that models have now been showing for a long time, will begin to take shape by the end of this week as heights in upper levels of the atmosphere begin falling in a retrogressing manner from the Atlantic westward into the eastern USA ( below ).
European 51-Member Ensemble Mean 500 MB Height Anomaly Forecast: Days 6-10
This occurs as the North Atlantic Oscillation tanks into a deep negative phase, and is actually a result of a major SSW ( Sudden Stratospheric Warming ) event that occurred back during early-mid February with a complete reversal of the wind field at 60 degrees North and 10 MB.
Zonal Mean Zonal Wind At 60 North and !0 MB
Note the dramatic temperature rise which occurred, into record levels, within the stratosphere from 60-90 degrees North Latitude ( below ).
Zonal Mean Temperature Between 60-90 N At 30 MB
This initially contributed to the stagnant SW upper flow pattern which produced flooding from the Cumberland Mountains west into the Mississippi Valley ( recently ).
European Model 10 MB Analysis At 7 AM – February 16, 2018
Now the polar vortex will be undergoing a location change and this will be changing the upper flow pattern across the Northern Hemisphere. Details are to be worked out and I am sure there will be plenty of model changes within the troposphere ( where longer-range forecasts are not as stable as within the stratosphere ).
European Model 10 MB Forecast At 7 AM On March 4, 2018
The Bottom Line….A wet pattern continues through this week with a trend toward colder air by late week into the first half of March ( up-down fluctuations ).
*Wintry chill felt Monday Night into Tuesday being driven by an influx of dry air and prime conditions for radiational cooling = low-level temperature inversion formation with cold air drainage into mountain valleys.
