... High pressure will remain southeast of our area today, allowing temperatures to return to remain around normal. A very strong Arctic cold front will push across the area Tuesday, bringing some snow to the mountains, and the coldest air to the region since February. Temperatures will moderate somewhat toward the end of the week, but remain below normal.
NEAR TERM /THROUGH TONIGHT/... As of 940 AM: No significant changes with this update; minor adjustments to T/Td trends and revised sky cover based on latest satellite imagery and blended fcst data.
Quiet weather on tap through this evening as mid to high clouds gradually increase ahead of the arctic front poised to push into the region late tonight. Light southwest winds with occasionally gusts to 20 mph will develop this afternoon in response to a tightening pressure gradient across the region due to weak cyclogenesis occurring along the arctic front across the Ohio Valley into the Mid-Atlantic states. Seasonably mild highs into the 60s are expected to prevail. The forecast becomes complicated in a hurry tonight as a unusually strong 1040+ mb arctic high dives south across the front range and drives a cold anafront through the region. Model guidance has trended a bit slower with the frontal passage, delaying the onset of precipitation until after midnight for most. The front itself will likely be on the move through the forecast area, possibly near the escarpment at the end of the near term period. QPF of one quarter to one inch will be common through 8 am Tuesday (focused across the mountains to Upstate of SC) with most of that falling in the form of rain below 4000 feet. The arctic airmass will support a rapid turnover to snow above 4000 feet between 2 am and 8 am with a couple of inches of snow possible above 5000 feet by the end of the period. Model sounding suggest that a brief period of sleet or freezing rain will be possible across the mountains, mainly between 4 and 8 am. This along with the potential for a flash freeze across the mountains, especially above 3500 feet will be watched closely. A strong surface pressure gradient nearing 10 mb across the mountains coupled with strong cold air advection will likely support northwest wind gusts of 30 to 40 mph developing across the mountains including Asheville. This combined with temperatures falling through the 30s will drop wind chill values into the 20s or colder.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 310 am Monday: Arctic front and attendant precip band will be moving through the forecast area at the start of the period, with pops ranging from likely across the mtns, to 90-100% across the Piedmont. Very cold air will be overspreading the forecast area in the wake of the front. Snow levels will fall continue to fall rapidly across the mtns throughout the morning, reaching the valley floors in all but perhaps extreme southern portions of the NC mtns. There will be sufficient overlap of cold air with moisture/forcing to result in at least a brief period of wintry precip across much of our mtns Tue morning, and in fact, we are now forecasting widespread measurable snowfall across the NC mtns, with totals ranging from dusting to one half inch across the valleys, to as much as 3 inches in the high elevations. This does not meet headline thresholds. However, one could argue that the early season nature of this event, along with the potential for "flash freeze" conditions above 3500 ft or so, as well as the potential for a brief period of sleet/FZRA goo before the transition to snow is completed could warrant an "impact-based" advisory. With the peak of any wintry weather concerns being more than 24 hours in the future, it seems prudent to allow the day shift to mull this one over a little more in collaboration with neighboring WFOs.
Otherwise, Tuesday's highs will occur at 12Z, with temps remaining steady or slowly falling after the initial cold air surge. This will mean afternoon temps struggling to warm above freezing across all but the lowest/most southern mtn valleys, while the Piedmont and foothills will generally see afternoon temps in the 40-45 range. NW winds gusting to 30 to 40 mph will also yield afternoon wind chills ranging from the teens and lower 20s in the valleys, to the single digits in the higher elevations, with wind chills falling into the single digits (or below 0 across the high elevations) across all of the mtns Tue night.
The remainder of the short term will feature temps a good 20 degrees below climo, along with very dry conditions and generally clear skies.
LONG TERM /THURSDAY THROUGH SUNDAY/... As of 3:35 am Monday: In the mean, long wave troughing will persist across the eastern Conus through the period. Temperature moderation will begin early in the period. However, temps are not forecast to return to normal at any point during the medium range. In fact, 5-10 degrees below climo is as close as they get. All global model sources continue to exhibit poor run-to-run consistency regarding the evolution of Southeast coastal cyclone development late in the week, although the ECMWF is beginning to show signs of making up its mind with the potential for a precip shield brushing our southern and eastern zones during the Fri/Sat time frame. Nevertheless, confidence in this scenario is very low at this point, and only slight chance pops are advertised in those areas during that time.