... An approaching cold front will bring a chance of showers to parts of the area today and tonight, perhaps with a few thunderstorms mainly in the North Carolina mountains. The front will exit the area Friday, resulting in dry and somewhat cooler conditions Saturday. Expect unseasonably warm weather to return Sunday, followed by periods of unsettled weather next week.
NEAR TERM /THROUGH TONIGHT/... As of 1010 am EDT: Regional radars are showing scattered shower coverage developing in and near the base of the southern Appalachians this morning ahead of an approaching cold front moving just east of the lower OH/mid MS River valley. Anticipate shower coverage growing in the NC mountains through the late morning and afternoon, and perhaps across northeast GA as well, but with a delayed push later this afternoon and evening east of the mountains just ahead of the frontal zone. Showers, albeit waning in coverage, should then transit the lower Piedmont tonight. Instability continues to look rather questionable during the afternoon and evening hours as soundings show warm mid levels persisting. The stronger upper forcing will remain northwest the area this afternoon, however, increasing bulk shear will make the case for a few stronger storms across the mtns and into NE GA late day. A couple storms could produce damaging outflow winds, yet most of the convective activity will be weaker. Rainfall amts with the front will be low as weak instability should limit rainfall rates. Max temps will be held to near normal levels across the mtn valleys due to higher cloud cover, while highs east of the mtns will be a couple degrees warmer than normal and abt 5 degrees warmer than that around the I-77 corridor. Mins will be held about 8-10 degrees abv normal tonight with patchy to areas of fog development likely across the NC mtn valleys before daybreak Friday.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 215 AM Thu: Cold front will remain across the lower Piedmont zones SE of I-85 Friday morning; a stray shower along it is not completely out of the question, but any such activity should exit the CWA during the morning, with the front. Diurnal destabilization along it is expected to be to our south and east. Weak upslope flow across the TN/NC border will probably produce abundant cumulus Fri aftn beneath a strong midlevel inversion associated with the incoming high; this looks too shallow for any mentionable PoP. CAA will occur via the same flow, possibly making for steady or slightly falling temps in high elevations during the day and breezy winds lasting into the overnight. Elsewhere CAA appears to be offset by lee troughing, keeping low-level winds westerly to southwesterly until Friday night when 500mb trough begins to lift out and sfc high shifts across the CWA. Temps Friday afternoon probably won't feel all that much cooler in the Piedmont, compared to Thursday. Mins Saturday morning however do look to trend 7-10 degrees cooler for most locations.
The surface high will migrate to the East Coast over the subsequent 24 hours, and cooler, more fall-like max temps are forecast for the whole CWA. This will be short-lived. Heights rebound quickly ahead of amplifying MS Valley ridge, and mins will trend warmer for Saturday night. Warm frontal activation does look to occur across the lower Ohio Valley at that time, but models are almost unanimous in showing the resulting precip staying west of our border thru 12z Sun, so our forecast will remain dry thru that time.
LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 300 AM Thu: A warm front will continue to develop in the middle Mississippi to lower Ohio valleys on Sunday, with shortwave crossing the Rockies and initiating cyclogenesis along the boundary and pushing it north. Closer to home, a flat ridge will persist across the Southeast along with the sfc high, which by then will have shifted offshore. We can now be more confident in a dry forecast for Sunday. Temps will be warm, with maxes 7-11 degrees above normal, and mins even moreso.
Models now are in better agreement on the shortwave moving east, reaching the southern/central Appalachians Monday or Monday night, and bringing with it the frontal system. A cold front looks likely to push across western KY/TN by the end of peak heating Monday. Respectable CAPE is progged in the warm sector of the system. Depending on how deep the shortwave is, the setup could end up favorable for severe weather to our west during the afternoon, with some of that activity possibly propagating into the CWA by evening, or at least the environment could become favorable east of the mountains. The 20/12z ECMWF depicted a pretty good high-shear low-CAPE setup across parts of KY/TN, but the new 21/00z run is a little less concerning. The GFS is showing more of a supercell environment. The shortwave currently is timed to cross the CWA overnight or early Tue morning, so we may escape some or all of the threat even if it exists to our west. Any threat Tuesday currently looks to be nearer the NC/VA coast. Of course, there is plenty of time for the timing details to change, and there remains a typical amount of model spread on the position of the shortwave and how far north it pulls unstable air. For now, Mon-Tue is worth keeping an eye on.
A shortwave ridge is expected to migrate across the area in the wake of the aforementioned system, and a lull in precip should occur across the CWA for a portion of the Tue-Wed timeframe, along with somewhat cooler (still above-normal) temps. Timing differences from ensemble members however warrant small continuing PoPs. Another deep shortwave or cutoff low will approach our area from the west near the end of the period, so PoPs ramp back up toward the end.