... A strong cold front will bring a chance of strong storms and brief heavy rainfall to much of the area this afternoon and early evening. In the wake of the front, cool and dry high pressure will build into the area and persist for several days. Seasonable temperatures and mostly clear skies will continue through the weekend.
NEAR TERM /THROUGH THURSDAY/... As of 235 PM EDT Wednesday: we're currently seeing a few bands of light to moderate showers streaming northward just east of the I-26 corridor and a much broader area of heavier showers approaching our westernmost zones from TN. Coverage will continue to increase from the west as the front moves into our CWA.
Otherwise, the mid/upper low will close off over southern IL and then move up the OH Valley and then northward toward the Great Lakes later tonight. The sfc cold front associated with the upper trof/low will finally move east of the fcst area this evening. Isolated strong to severe thunderstorms remain the main concern ahead/along the cold front over the next few hours, but so far we haven't seen any storms get very strong. Sfc-based CAPE remains fairly modest...upwards of 1500-2000 J/kg over the eastern zones with less the farther you go west. We also lack a low-lvl jet, which keeps the deep-lyr shear relatively weak, maybe 25 kt at best. The Marginal Risk for the Day 1 Outlook from SPC still looks pretty good. The QPF still does not look high enough to suggest a flood threat and storms should continue moving at a good clip thru the CWA. The precip shuts off quickly from west to east behind the front this evening, except in the WLY to NWLY flow upslope areas along the TN border, where some light precip could linger into early Thursday. The cooler and drier air will steadily filter into the region behind the front overnight, such that low temps Thursday morning should be about 15 degrees cooler than the last few nights.
SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY NIGHT/... As of 1130 AM Wed: High pressure will dominate the pattern over the CWA through the weekend. By the start of the period Thursday evening, the high will be centered just west of the mountains, but the gradient will have become weak so winds will be generally calmer overnight. Thus, min temps will trend cooler, and most guidance depicts Friday morning as being the coolest of the next few days, mostly 7 to 10 degrees below normal. Ridgetops still look to fall into the 30s, with patchy frost not out of the question at those highest elevations. While partial thicknesses will continue a slow rebound, the high does center east of the mountains by Saturday morning. Weaker low-level winds may allow slightly better radiation and decoupling then, so some areas could see temps "crater" and end up cooler than the previous morning, but in general should be a degree or two warmer.
Model runs show some spread in timing the arrival of a shortwave which will rotate through the longer upper trough to our north. The shortwave will be associated with a reinforcing cold front which will bring a shot of precip to the Ohio Valley. The consensus of guidance is for a dry fropa in our CWA; only a few ensemble members depict any precip reaching the NC mountains. No PoP will be included thru Sunday night.
LONG TERM /MONDAY THROUGH WEDNESDAY/... As of 1230 PM Wed: A second dry anticyclone will build across the area in the wake of the cold fropa circa Sunday. Heights will rise at least briefly, and partial thicknesses continue to rise as the airmass modifies. Thus we appear on track for max temps to climb back a few degrees above normal Monday and Tuesday. As a sharp ridge develops over the Plains, amplifying trough over the East may drive another shortwave and/or cold front in our direction Wednesday, but for this forecast cycle we will be able to maintain a dry forecast through the end of the period.