020716 Forecast

My Forecast For Today ( February 7 )

ALERT For Accumulating Snow Monday-Wednesday With Bitter Cold Temperatures Tuesday-Wednesday

Abundant moisture will combine with very cold air aloft to produce snow, heavy at times, during a prolonged period beginning Monday and continuing through Wednesday.

Overnight Into Sunday Morning

Cloudy skies giving way to clearing into the predawn to morning hours.  Light SW winds shifting N at 5-10 mph on middle elevation ridges-plateaus below 2700 feet.  N winds 5-15 mph, with higher gusts, along upper elevation ridges.  Temps dropping mostly into the 20s ( variations from 10s in colder valleys, if skies clear during the predawn, to upper 20s-lower 30s along exposed mid-upper elevation ridges ).  Wind chills in the 10s & 20s ( coldest at highest elevations ).

Super Bowl Sunday Afternoon

Sunny with a chance for high clouds late.  N-WNW winds at generally less than 10 mph.  Temperatures varying from the lower-mid 30s in highest elevations of the High Knob Massif to the mid-upper 40s.

Tonight Into Monday Morning

Partly to mostly clear during the evening.  Increasing clouds overnight into morning with a chance for flurries and light snow developing.  SSW-SW winds 5-15 mph, with higher gusts, along mid elevation ridges & plateaus below 2700 feet.  SW-WSW winds increasing to 10-20 mph, with higher gusts, along upper elevation mountain ridges above 2700 feet.  Temperatures mostly in the 20s to lower 30s.  Wind chills in the 10s & 20s ( coldest highest elevations ).

The most significant snowfall accumulations Monday, during the period from 8:00 AM to 4:00 PM, are favored along and southwest of the High Knob Massif & Tennessee Valley Divide on SW Upslope Flow ( e.g., Norton-Wise & Sandy Ridge southwest to Big Stone Gap and Lee County verses lighter amounts from Pound-Clintwood to Haysi-Grundy where some mix may occur ).  Updates To Come.
Widespread snow, with embedded bursts of heavy ( whiteout ) snow will be possible from late Monday into Tuesday across the entire area, with heaviest amounts in general favoring W-NW facing slopes along the Cumberland Mountains and Blue Ridge.


Weather Discussion ( February 6-7 )

How would you like to photograph in a place where a bear uses an electrical pole as his scratching post?  To see more photographs reference The High Knob Landform website.

Scratching Post For Mr. Hoss
Scratching Post For Mr. Hoss – High Knob Massif

A seasonally cold Saturday was felt across the mountain area with morning MINS in the 10s, amid colder mountain valleys, and 20s along exposed ridges.  The afternoon was dominated by sunshine that gave way to high clouds with temperatures varying from near 30 degrees at summit levels of the High Knob Massif to upper 30s-mid 40s.

Sunset View From Stone Mountain
Sunset View From Stone Mountain In Lee County – February 6, 2016

While snow may not yet be on the mountains, my friend Rodney Parsons submitted a great sunset view from the top of Stone Mountain in northern Lee County ( with some visible wave clouds to boot ).

Nora 4 SSE - Site of Official NWS Station - Elevation 2650 feet
Nora 4 SSE – Site of Official NWS Station – Elevation 2650 feet

Temperatures on this Super-Bowl Sunday will become a little milder than Saturday, but remain chilly, in advance  of a cold front that ushers in weather changes Monday.

NAM 12 KM Model Surface Streamlines and Mean Sea Level Pressure
NAM 12 KM Model Surface Streamlines & Mean Sea Level Pressure – 10 AM Monday
Flow will be SSW-WSW in advance of a cold front from Monday morning through early-mid afternoon, which will tend to favor locations along and southwest of the High Knob Massif and TN Valley Divide for the most snow ( verses downslope locations in river basins of the Russell Fork and Levisa Fork ).
GFS Model 500 MB Temperature Forecast
GFS Model 500 MB Temperature Forecast – 7 PM Monday ( February 8 )

A key to this forecast, regardless of what model one looks at, is very cold air aloft and abundant moisture vertically by later Monday into Tuesday.  This supports widespread snow with embedded snow squalls ( bursts of heavy snow ) that could cause whiteout conditions at times.

*Temperatures aloft at around 17,000 feet are forecast to plunge into the -32 to -36 Celsius range ( -26 to -33 F below zero ) by late Monday into Tuesday.  This will generate steep lapse rates in the vertical ( i.e., rapid drops of temperature with increasing height ) and make the lower atmosphere unstable ( absolutely unstable with respect to air parcels ).
GFS Model 500 MB Temperature Forecast
GFS Model 500 MB Temperature Forecast – 7 AM Tuesday ( February 9 )

Past climatology of the High Knob Massif area shows that heavy snow tends to develop and fall when temperatures aloft become this cold with available moisture.  Otherwise, the flow trajectories are not shown to be from the Lakes on most models until beyond this period for the southern Appalachians ( the lake connected flow remaining from West Virginia northeastward along the mountain chain ).  This needs to be followed and updated on new forecasts.

If later Great Lake connected flow follows, either by mid-week and/or later by next weekend ( when the coldest air mass of the winter season potentially arrives ), this would add greatly to total snowfall amounts along the upslope side of the mountains with potential for very heavy totals in the High Knob Massif.
In a prolonged snowy period like upcoming, total snowfall amounts are likely to be greater than snow depths at any given point in time ( outside of drifting ) due to some melting-sublimation and settlement of snow.

The Bottom Line…A prolonged period of snowy and increasingly colder weather is upcoming this week from Monday through Wednesday-Thursday.  Bitter temperatures are likely during Tuesday-Thursday, with potential for a reinforcing blast of even colder air by this next weekend ( stay tuned for updates ).

**Reference my latest Extended Outlook for details.

Make it a great Super-Bowl Sunday.