... A large area of high pressure will build over the eastern United States this weekend into early next week. This will bring cooler and dry weather to the region during this time.
NEAR TERM /THROUGH SUNDAY/... As of 700 PM EDT Saturday...
Across much of the region, opaque high level cloud cover was observed with the northern extent of it more scattered and thin. The only low clouds of note were over parts of the Northern Mountains and Foothills of North Carolina. As drier air continues to work its way into the area, this lower cloud cover will dissipate. The high level cloud cover is expected to thin and shift southward as the night progresses, leaving clear skies for all areas by daybreak Sunday. Special 18Z KRNK sounding showed very dry air from 800mb and upward, with only 0.31 PW values and 850mb temps around +4C. As winds continue to weaken through the night, cloud cover decreases, and surface dew points also decrease, we will be looking at a cool night. The mid to upper 30s will be common across the mountains with lower to mid 40s across the Piedmont. Have made some minor tweaks to the forecast low temperature, and decreased winds a little in some of the valleys. Dew point depressions still look too wide with temperatures not quite cold enough, and still plenty of leaf canopy to include much in the way of frost for the area. However, if any is to form, the locations with the best potential include parts eastern Ashe County NC into far western parts of Alleghany County NC, and also central Bland County VA within a narrow hour or two window just prior to sunrise.
As of 110 PM EDT Saturday...
An upper level trough hovering over a classic cold wedge had mostly cloudy skies draped across the region today. These clouds along with cold air advecting in from the north has kept the area rather chilly. High temperatures so far today was in the mid 50s to lower 60s which is around 15F cooler than normal.
The trough will eventually move east of the area tonight, allowing more dry cold air to move into the region. Skies will become clear overnight and should remain sunny through the day. Some fair weather cumulus clouds may form over the mountains in the afternoon, but no rain is expected to fall.
Overnight lows will be colder than this morning as temperatures drop into the 40s, some 30s in deeper mountain valleys. Some patchy frost is possible in non-canopy areas, but coverage not widespread enough for a frost advisory.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 100 PM EDT Saturday...
Confidence is high that high pressure covers our region through the short term period of the forecast keeping dry conditions in place. Temperatures will gradually moderate through the period, as low level temperatures 1-2 standard deviations below average on Monday morning climb to near normal values by Tuesday, as high pressure at the surface weakens.
Introduced some isolated areas of patchy frost across some of the mountain valleys (like Burkes Garden) for Monday and Tuesday morning with good radiational cooling conditions expected combined with an abnormally dry air mass. Due to these conditions, a couple of degrees were shaved from low temps forecast by the National Blend of Models forecast.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 100 PM EDT Saturday...
A return to normal to even slightly above normal temperatures are expected late this week as the large area of surface high pressure over our area weakens and drifts southeast, allowing for a weak low level south/southwest flow. There is considerable uncertainty regarding the timing and strength of a cold front that will approach our area late in the week. The 06Z GFS is much stronger with this system and forecasts a brief surge of cooler air. This is an outlier compared to individual ensemble members in the GEFS and was ignored. As a result, kept the forecast dry for the entire work week, but introduced widely scattered showers on Saturday as low level moisture returns.