... Wintry precipitation will return across the mountains and over the northern foothills and piedmont of North Carolina tonight as a strong and cold upper disturbance crosses the area. Canadian high pressure will return dry, cold conditions Thursday through Saturday, before a moist cold front and associated precip arrives from the west Saturday night into Sunday.
NEAR TERM /THROUGH THURSDAY NIGHT/... As of 6:50 PM EST Wednesday: Sct to numerous rain showers are currently overspreading the fcst area from the west as cigs have lowered over most sites. Still expecting the light to moderate precip to make its way over the area into the overnight hours and then move east of the CWFA after about 06z, although showers could linger a bit longer over our far eastern zones.
Otherwise, no major changes to the 12z model guidance and to our overall thinking for tonight thru Thursday. Strong DPVA associated with a passing upper trough will cross right over the forecast area tonight, with peak forcing in the 03z-09z time frame. Moist upglide should spread an area of rain across the area this evening, shifting east during the pre-dawn hours. A sfc low is progged to develop over the Carolina Piedmont and strengthen as it shifts east to south of the Outer Banks by 12z Thu. A deformation zone precip shield is still expected to develop, while strengthening NLY CAA flow brings low-level thicknesses down across western NC. As dynamical cooling and CAA peak during the pre-dawn hours, rain should mixed with and/or change over to snow across the NC Piedmont. QPF has perhaps ticked up a tad from previous model runs, but sfc temps will be on the warm side, and should limit snow accums. Even if we get toward advisory-level snow of 1-2", impacts on roads should be limited due to warm surfaces. So with all that in mind, have opted not to expand the advisory beyond the current Davie County at this time. But Iredell and Rowan do still stand a chance of those 1-2" amounts if things line up right. Meanwhile, NW flow should continue to force some snow activity along the TN border, with snow showers tapering off by noon Thursday. With the low deepening off the coast and high pressure building in from the west, should see windy conditions across the forecast area Thursday morning, with winds beginning to weaken in the aftn. A NAM cross section shows a mountain wave signature, and so will could see 40-50 mph gusts along the escarpment and in the high terrain. Winds are being mentioned in the WSW as well. Temps are expected to drop into the 20s across the mountains and low to mid 30s across most of the Piedmont by daybreak Thursday. It will be sunny Thursday, except lingering clouds along the TN line, with temps ranging from the 20s above 3500 ft, to the lower 50s in the Lakelands.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 230 PM Wednesday...GFS and ECMWF both indicate trough continuing to push off New England/Mid Atlantic coast entering short term as a broad 500mb ridge pushes into area. Heights rise as a broad ridge approaches from the west and dry cP air drops in from the north. Initially north-northwesterly flow shifts to southeasterly as the sfc high center passes out to the Atlantic, drawing in additional moisture. Saturday, increased forcing from an approaching shortwave to the west will generate increasing sky cover over the course of the day, but don't expect significant PoPs until Saturday night into Sunday, probably in the 00Z-06Z window. The GFS anticipates more midlevel prefrontal moisture and thus predicts a slightly earlier onset than ECMWF.
Extremely low RH through the lower and midlevels and clear skies should allow radiative cooling both Thursday and Friday night; temps should be in the 20s or lower on Friday morning and should drop well below freezing overnight into Saturday.
LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 230 PM Wednesday...onset of precip will be Saturday evening, depending on placement of best moisture and timing of shortwave trough the region, which GFS and European models still disagree on. ECMWF still shows a coastal low developing and passing south of our CWA, which introduces a threat of winter wx, though it's still too far out to pin down any details. GFS leans more into the coastal low setup as of the 12z run. Either case is likely to produce some snow showers in the mountains but if ECMWF guidance pans out then this could extend into the NC Piedmont.
In any case, chilly temps will stay in place through Tuesday, before a new upper system approaches from the west. Models diverge greatly as far as timing and dynamics of this system.