ALERT Remains In Effect For Dense Fog Into The Overnight Along Mid-Upper Elevation Ridges And Plateaus ( Cloud Bases Lifting Off Mid-Elevations Toward Morning – Patchy Dense Fog Other Sites )
ALERT For Strong SSE-SSW Winds From This Afternoon Into Wednesday Morning – In Advance & Along A Line Of Potentially Strong-Severe Storms
Strong winds are expected across the entire area but with enhancements along high mountain ridges and in typical mountain wave breaking zones ( e.g., Powell Valley of Wise County & Clinch River Valley of Russell-Tazewell counties in southwest Virginia & along Pine-Black Mountain in SE KY ).
ALERT For Heavy Rain Potential & Strong Rises On Creeks In The Midnight-Noon Period of Wednesday
The threat for strong rises on creeks will be greatest in those draining the High Knob Massif where snow melt has steep creeks gushing with water tonight, and in any locations that might have downpours in thunderstorms during the Midnight to Noon period on Wednesday ( February 3 ).
Overnight Into This Morning
Dense fog along middle-upper elevation ridges-plateaus giving way to patchy fog at lower-middle elevations as winds shift from northerly to SE to SSW at 5 to 15 mph. Temperatures nearly steady in the 40s ( or slowly rising into morning on mid elevation ridges & plateaus ).
Partly to mostly sunny. Warm & windy. SSE winds 10-20 mph, with higher gusts, below 2700 feet. SSE to S winds at 20-30 mph, with gusts to 40+, on upper elevation ridges. Local mountain wave gusts becoming possible. Temps varying from 50 to 55 degrees in upper elevations of the High Knob Massif to the upper 50s to middle 60s ( some upper 60s possible amid downslope communities of the Russell Fork & Levisa Fork basins from Pound to Grundy ).
Tonight Into Wednesday Morning
Increasing clouds with showers & thunderstorms becoming likely during the midnight-sunrise period. Strong to locally severe storms possible. Windy. SSE winds 20-35 mph, with higher gusts, below 2700 feet. SSE-S winds 30-40 mph, with gusts of 50-60+ mph, along upper elevation ridges ( locally severe winds to 60+ mph also possible in mountain wave zones ). Unseasonably warm & humid. Temperatures varying from upper 40s to the upper 50s.
Weather Discussion ( February 1-2 )
The new month of February is wasting little time in getting active, with the first weather system spreading rain across the mountain area during Monday.
Cloud bases dropped as low-level winds shifted northerly. This was well predicted in advance by my forecast last night ( reference my 020116 Forecast for details ).
During the evening some especially dense sections along U.S. 23 included Little Stone Mountain Gap, near Powell Valley Overlook, and the Wise Mountain section at the head of Indian Creek.
These clouds will remain on the ground in mid-elevations as long as low-level winds possess a northerly component, and will linger after that if the shift to SSE-SSW winds remains light enough overnight to minimize downsloping ( valleys will tend to have dense fog in places ).
This shift to southerly winds has now occurred along high crest lines which also remain obscured in orographic pilatus clouds.
Snow melt has produced a steady increase in water levels on steep creeks draining the High Knob Massif since beginning on January 26, with a recent peak to above “Red Alert” level indicating a gush ( ROAR ) of tumbling whitewater.
This prolonged period of snow melt run-off is not surprising given the snow cores that I took in the High Knob Massif. Reference the updated My High Country Focus section for more details.
Focus now shifts to a major storm system that will begin impacting the Mountain Empire later today as the pressure gradient begins to CRANK winds. Severe non-storm related gusts will become possible from late today into Wednesday.
Meanwhile, the highest risk for severe thunderstorms will remain west and southwest of the Appalachians; however, this will need to be closely followed as a strong to locally severe thunderstorm can not be ruled out ( main threat being enhanced transfer of severe winds aloft down to surface layers ) as the main squall line reaches the area between Midnight and Sunrise on Wednesday.
Outside of the strong wind threat, with possible tree damage and downed power lines, the focus will be on where do main bands of heavy rainfall set up. The models differ on this and often have trouble with convective rains ( like with orographic precip ).
Given recent snow melt, and ongoing melt, we must hope to keep downpours at a minimum as this system rolls across the area.