Mountain Area Forecast ( October 6-8 )

*An ALERT For Dense Fog Formation May Be Needed For Middle-Upper Elevations Along & North Of The High Knob Massif-Tennessee Valley Divide Friday Night Into Saturday

*One or more nights with potential of frost formation is being watched for mid-upper elevation mountain valleys next week.

Overnight Into Thursday Morning

Mostly clear.  Chilly.  Areas of valley fog.  SSE winds 5 to 10 mph, with some higher gusts, along middle-upper elevation mountain ridges.  Temperatures varying from upper 30s to lower 40s in colder mountain valleys to upper 40s-low 50s.

Thursday Afternoon

Mostly sunny.  Pleasant.  Winds E-SE at 5-10 mph.  Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s.

Thursday Night Into Friday Morning

Becoming partly-mostly cloudy.  Winds ESE-SE at 5-20 mph, with higher gusts, on middle to upper elevation mountain ridges.  Temperatures varying from the mid-upper 40s to the upper 50s ( warmest on exposed mid elevation ridges ).

Friday Afternoon

Mostly cloudy.  ESE-ENE winds mostly less than 10 mph.  Small chance of a shower or sprinkle.  Temps varying from upper 50s to lower 60s in upper elevations to the upper 60s to lower 70s ( warmer in the Great Valley all these days ).

Friday Night Into Saturday Morning

Rain showers & rain developing.  Winds shifting NE-N and increasing to 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges-plateaus.  Cloud bases dropping with dense fog on higher ridges ( possibly down to the level of Wise ).  Temps dropping into the 50s to around 60 degrees by morning ( 40s wind chills at highest elevations ).

Saturday Morning-Afternoon

A chance of rain showers-drizzle.  Windy & chilly.  Low cloud bases with dense fog above 2500-3000 feet along and north of the High Knob Massif & Tennessee Valley Divide.  Becoming partly cloudy late.  Winds N to NE at 15-25 mph, with higher gusts.  Temps steady or falling in the 50s lower-middle elevations and dropping to the 40s-low 50s in upper elevations.  Wind chills in upper 30s to lower 40s at highest elevations.  Milder conditions lee of the High Knob Massif into river valleys of the Clinch, Powell & Holston drainages. 

 

Weather Discussion ( Chilly Weekend )

Thursday Evening Update

As CAT 4 Matthew gets closer to the Florida coast I have updated to define conditions here through Saturday PM.

Some significant rain will rotate west-northwest into the Appalachians Friday Night-Saturday, with a sharp cut-off likely near or just southwest of the High Knob Massif and Tennessee Valley Divide.  The heaviest rains are expected generally along and east-southeast of the Blue Ridge, with at least the chance for some heavier amounts in favored orographic locations with increasing upslope along the western side of the mountain chain.

The timing between arrival of a cold front, from the west, and moisture wrapping around the broad circulation of Matthew will help to dictate where the heavier downpours develop.

The NAM Model group is wanting to develop rain along the Appalachians as moisture interacts with a cold front from the west, with a sharp cut-off producing little to no rainfall in foothills of Kentucky westward of the mountains.  This will bear watching given the increasing upslope along the western side of the mountain chain from enhanced flow around Matthew ( i.e., an increasing pressure gradient ).

Regardless of local rain amounts, cloud bases will be dropping on increasingly gusty NE-N winds into Saturday with upsloping and chilly conditions expected ( especially for locations along and NE-NW of the High Knob Massif and Tennessee Valley Divide ).  Skies will become partly cloudy, then clear, as drier air invades later Saturday into Sunday ( with windy conditions continuing ).

The Bottom Line…A very chilly weekend is ahead for the mountains with the first true wind chill factors of the autumn season expected across higher elevations as a cold frontal passage combines with an increasing pressure gradient around Matthew.  Rain & low clouds  ( dense fog at higher elevations ) into Saturday giving way to clearing, gusty conditions later Saturday or Saturday Night-Sunday before conditions calm. 

 

Previous Discussion

Temperatures are chilly in mountain valleys tonight, with 40s to lower 50s at Midnight Thursday, as sinking air north of Hurricane Matthew is drying the vertical column.

Reference Mid Autumn 2016 In The High Knob Massif to view a  few shots of changing autumn colors in the high country.

The effect being further enhanced with SE-SSE downsloping along the western side of the Appalachians at low-levels.

Hurricane Matthew is looking better organized on IR imagery in recent hours, after passing Cuba & Haiti, and continues wobbling toward the northwest ( the wobble due to fluxes in convection ).

The current National Hurricane Center track forecast is closely following the 51-member European Ensemble MEAN.

Meanwhile, back here in the Appalachians the current indirect influences from Matthew will become a little more notable into Friday Night-Saturday as the pressure gradient increases.  Windy conditions and dropping cloud bases will develop along the mountains on upsloping northerly flow to generate chilly temperatures and some showers-drizzle   ( the greatest coverage of showers-rain is expected along and well east of the Blue Ridge ).

Saturday could be a very chilly day along and north-northwest of the High Knob Massif and Tennessee Valley Divide, with temps in the 50s dropping into the 40s at upper elevations ( temps falling into the 50s at lower-middle elevations ).  Windy conditions will make it feel colder, especially along mountain ridges-plateaus.  Stay tuned for updates.