327 FXUS62 KGSP 210153 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 953 PM EDT Fri Aug 20 2021 .SYNOPSIS... Scattered showers and thunderstorms chances will continue into the early evening hours. Subsidence aloft associated with a ridge of high pressure over the south-central CONUS will slowly build eastward into the Carolinas and Georgia leading to drier conditions this weekend and early next week. The upper-level pattern will remain relatively unchanged during this time. Isolated showers and thunderstorms will remain possible this weekend into early next week. && .NEAR TERM /THROUGH SATURDAY/... As of 745 PM EDT Friday: What little convection took place today has died off, leaving a field of widely scattered midlevel clouds and mainly clear skies across the CWA. Overnight, as dry air continues to filter in from the north, the upper levels should become dry enough to support at least patchy fog development. Although a few of the models are predicting fog outside the mountains, the odds seem reduced for much of a reduction in visibility given that so little rain has fallen and the PBL will be a good amount drier than anticipated. Indeed, it may be primarily our mountain sites at risk of fog in the early morning hours. Saturday, as a deepning upper low begins to pivot east of the CWA, heights should hold stable or even begin to rise slightly by afternoon; thus, synoptic forcing will be weak/nonexistent. This combined with dry mid/upper levels should severely hinder convective initiation tomorrow, and so we should see even more anemic thunder activity Saturday afternoon than we have today. A few pulse storms may pop up, along with isolated to widely scattered showers, but for the most part, below-climo convective activity is in the works. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 2:15 PM EDT Friday: Throughout the short term forecast period, a ridge of high pressure will build across the south-central CONUS while a closed low over the Mid-Atlantic interacts with Tropical Storm Henri out in the western Atlantic. The ridge of high pressure will gradually build eastward into the CWA this weekend into early next week. As a result, the closed low will be forced northeast of the Carolinas, gradually tracking towards New England through early next week. This ridge of high pressure will lead near normal PWATs and mainly NW'ly flow this weekend into Monday allowing for much drier conditions. With no real synoptic forcing in place, daytime heating will be the driver of diurnal showers and thunderstorms. However, with limited moisture available across the forecast area, only isolated showers and thunderstorms are expected throughout the short term so capped PoPs to a slight chance to chance. High temps should be roughly 4 to 8 degrees above Climo Sunday and Monday. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 230 PM EDT Friday: The eastern periphery of the ridge remains over the Carolinas and Georgia at the beginning of the extended forecast period, but retreats back west middle of next week. This will allow the Bermuda high in the Atlantic to extend over the southeast CONUS. So the overall synoptic pattern middle of next week will have the Carolinas and northeast Georgia sandwiched between two high pressure systems. This will lead to increased moisture and the continuation of above climo high temps. PWAT values will increase Tuesday ranging from 1.70 to 2.0 inches. These values are expected to linger over the CWA through the end of the forecast period. Tuesday into Wednesday shower and thunderstorm chances increase due to a surface trough draped over the central Carolinas. This sfc trough should remain over the Carolinas throughout the extended. Both the GFS and ECMWF show the two ridges of high pressure working together to bring a tropical wave into the Carolinas Thursday into Friday. This would further increase shower and thunderstorm chances middle to end of the workweek. Confidence on the track of this tropical wave remains fairly low as this occurs towards the end of the extended forecast. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsehwere: The isolated convection over our CWA earlier this evening has died off, leaving behind VFR conditions across the board. Should see scattered to broken sky cover overnight, with a lingering chance of some morning fog at mountain sites. Given that none of our sites have received rain, chances seem somewhat reduced, but the signal is still present in the MOS products, and mid levels are trending dryer, so have kept mention of some MVFR VSBYs at KHKY dropping to IFR at KAVL. Otherwise, a chance for isolated to widely scattered convection tomorrow, with initiation time delayed and intensity hindered by dry air aloft. For now, have only thrown in PROB30s for SHRA at each site mid-afternoon. Outlook: A typical, diurnal summertime convective pattern is expected to prevail the rest of the weekend and into early next week, with coverage scattered at best. Mountain valley fog will be possible each morning, especially for sites that received rain the previous afternoon. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...AP NEAR TERM...MPR SHORT TERM...AP LONG TERM...AP AVIATION...MPR