... Dry high pressure continues through mid week. A cold front sweeps across the area Wednesday evening, before an increasingly unpredictable but active pattern sets in for the weekend, potentially producing another round of winter weather.
NEAR TERM /THROUGH TONIGHT/... As of 625 am Tuesday: Cloud tops continue to warm within the NW/upslope flow regime near the TN/NC border, and all indications are that -SHSN have finally dissipated across the mountains. As moisture continues to deplete across the Great Valley of east Tennessee and western slopes of the Appalachians, skies should clear completely by late morning, giving way to sunny skies across the entire CWA for much of the day. Upper heights will otherwise rise today as trough continues to pull away from the East Coast. Resultant increase in thickness values will allow temperatures to warm above yesterday's reading, esp over the mountains, where it should be around 10 degrees warmer than on Monday. These temps along with sunny skies will yield good melting conditions across much of the area this afternoon. However, any lingering wet roads will likely refreeze tonight, as good radiational cooling and dry conditions should allow min temps to dip into the 20s in all areas. One more night of a "black ice SPS" will probably be needed before last weekend's winter storm is finally put to bed.
SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/... As of 210 AM EST Tuesday: Not much overall change to the short term forecast. Broad, flat ridging will remain in place on Wednesday, keeping conditions dry and allowing morning temps to drop 4-6 degrees below normal outside the mountains. Deterministic guidance continues to depict the a stout 500mb trough axis entering the Ohio Valley by Wednesday night, with DPVA forcing ramping up from 00Z to 06Z Thursday, and an associated moist cold front crossing the region overnight.
Onset of mountain precipitation is currently on track for 21Z Wednesday or so, with the majority of this being rain. Wetbulbs do support a changeover to snow at the higher elevations, before scant daytime warming will be enough to change most precip back to rain or a rain-dominant rain-snow mix Thursday morning. The approach of a much more potent upper trough out of the west late Thursday should allow forcing to ramp back up, continuing the rain through Thursday and possibly allowing for additional snow on Thursday night.
LONG TERM /SATURDAY THROUGH MONDAY/... As of 230 AM EST Tuesday: An active extended is in store as models come into better agreement about a potent system entering the eastern CONUS over the weekend. Deterministic guidance is struggling to handle the system consistently, with the last 2 runs of the ECMWF finally converging on a strong cyclone affecting the Carolinas, even as latest run of the GFS begins to diverge from this solution. The CMC has consistently depicted a solution in line with the latest ECMWF. Such a solution would result in cyclogenesis along a stalled frontal boundary south and east of the forecast area, in turn producing a cyclone that shifts east too quickly to appreciably warm 850mb temps. So, precipitation develops atop bitterly cold low-level air, resulting in an all-snow solution throughout Friday night and much of Saturday.
About 75% of GEFS members now depict some amount of wintry precip occurring with this system, indicating the latest dry solution from the deterministic run is an outlier; nonetheless, there remains significant uncertainty with the timing and intensity of this system, as well as what, if any, accumulations could be expected should another winter system actual materialize.
In any case, the upper pattern becomes much less perturbed behind this system, and cold, dry air builds in at the surface. A weak reinforcing cold front should arrive Monday evening, but looks too dry to warrant any PoPs.