Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
780 FXUS62 KGSP 201100 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 700 AM EDT Wed Aug 20 2025 .SYNOPSIS... Showers and thunderstorms are expected only over the mountains and foothills this afternoon and evening, but chances return to all areas Thursday, and increase heading into the weekend. Temperatures start out near normal then fall below normal for the weekend. Cooler and drier conditions develop early next week after a cold front crosses our region. && .NEAR TERM /THROUGH TONIGHT/... As of 5:15 AM EDT Wednesday: We remain shower free early this morning with light to calm winds across the area. Since the overnight hrs, low stratus has been gradually spreading southward from the higher terrain and westward from Raleigh`s area. It remains unclear exactly how far south/west these clouds will spread, but it`s looking like they will cover the bulk of our CWA before the morning is over. We`ve also been seeing patchy fog at a handful of sites, with the lowest visby`s re- ported in the mtn valleys. Low temperatures will be mild again this morning with values remaining a few degrees above climatology at most locations. Otherwise, stout upper ridging will remain centered to our west thru the near-term period. Long wave upper trofing over SE Canada will dig southward over New England today, allowing for minimal height falls across our fcst area. At the sfc, broad high pressure will slowly move off the New England Coast today as a wedge-like pattern continues to dissipate over the western Carolinas. At the same time, broad high pressure centered over the Great Lakes will slowly shift eastward and push a weak sfc boundary into our CWA today. Hurricane Erin will approach the Carolina Coast later to- night and then being to track NE by the end of the near-term period early Thursday. Overall, we can expect another active day across the mtns with sct to numerous showers and thunderstorms later this afternoon and evening. It remains unclear how far south and/or east any convection will develop today/tonight, but the further you go south and/or east, the lower the PoPs. Like the past few days, the severe potential looks minimal across our area, however an isolated flooding threat will exist especially over the mtns. With the dissi- pation of the wedge pattern and less cloud cover this afternoon, temperatures should rebound a fair amount today with highs fcst to be near-normal (if not slightly above) for mid-August. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 1220 AM Wed: A narrow band of vorticity and weak cold front will settle into the CWA Thursday, extending from the shortwave moving off the East Coast as it picks up the circulation around Erin and leads to the storm moving back out to sea. N to NE winds in low levels will be associated with moisture advection and some pooling along the front look to occur. Profiles will be weakly unstable and near-climo PoPs will be advertised: 20-30% in the I-85 corridor and 40-60% over the mountains. Chances have trended slightly lower, and skies slightly clearer in the model blend, so temps are now fcst to remain slightly above normal. Slightly rising heights and sfc ridging in the wake of those features will promote a turn to more easterly winds Thu night which could kick off elevated convection, so most areas east of the Blue Ridge Escarpment still feature chance PoPs thru the night. Slight drying may occur in our north so the best overall chances appear in the Escarpment areas south of US 74 and over the western Upstate. Locally heavy rain will remain a concern with any convection given westerly upper level flow but only weak or slightly easterly flow thru the midlevels, suggesting slow storm motion and/or some anchoring along E or SE facing terrain. On Friday several guidance members depict the sfc high setting up east of the Appalachians. The boundary by then should be effectively south of the CWA, and the progression of the high suggests a more typical quasi-stationary frontal regime with some degree of southerly upglide. 500mb trough overhead will help keep unstable profiles across the CWA, but most favored over the mountains/Escarpment. Widespread cloud cover should persist thru the day, which looks to knock temps back several degrees. Maxes end up 3 to 6 below normal over the Piedmont but still near normal in the valleys west of the Escarpment. The upglide or upslope flow will continue weakly Friday night but by then the trough axis should be in a less favorable position to enhance convection, so PoPs decline slowly, best chances being in the southern half of the CWA. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 100 AM Wed: Not much change to the thinking for Saturday; only subtle changes to the pattern are expected. Flow will turn slightly more southerly over the stalled front and the moist layer on prog soundings is shown to deepen, with instability still tempered by nearly moist-adiabatic lapse rates. Precip chances increase 5-10% compared to Friday with similar, still below-normal temperatures. Excessive rainfall will remain a concern with convection likely to be slow-moving and possibly anchoring, though the likelihood of flooding may be mitigated by the highest PWATs being south of the mountains, nearer the front. Heights fall over our region by early Sunday as vort lobe rounds the upper low centered over Ontario; the surrounding trough phases with what`s left of the baggy SE CONUS trough. GFS, for one, spins up a compact coastal low as the trough phases, but tracking such that minimal impact on sensible weather is expected for our Piedmont. Less of a mountain-Piedmont gradient in PoPs is forecast with the incoming trough veering winds to westerly in the mountains by peak heating, but suggesting lee trough helping to spawn convection in the Piedmont. Northwest flow and substantial mid to upper level drying develops by Monday so most areas currently receive a dry fcst that day. Min temps may trend slightly cooler Monday morning over the mountains, but maxes east of the mountains will trend slightly warmer again. Cool post-frontal air will settle over the area Monday night with mins and maxes Tuesday a few degrees below normal, but with dewpoints drying into the 50s that day as well; dry fcst once again. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: Another round of low stratus is spreading over our fcst area this morning cigs ranging from LIFR to MVFR at most terminals. MVFR visby is also being reported at numerous sites. This stratus is expected to be slow to sct and lift this morning, with at least MVFR ceilings fcst to linger thru much of the morning with an eventual return to VFR by the afternoon at all taf sites. Expect another round of afternoon/evening convection over the mtns, with a TEMPO for TSRA carried at KAVL and PROB30s for TSRA at all the other taf sites except for KCLT, where PoPs are too low to men- tion. Winds will be light thru the period and mainly out of the NE, but they could be VRB at times. At KAVL, winds will be light thru the period, but generally favor a NLY to NWLY direction. Outlook: Sct to numerous afternoon/evening showers and thunderstorms and their associated restrictions are expected across the fcst area Thursday and Friday. Morning fog and low stratus will also be possible each day, especially in the mtn valleys. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...Wimberley NEAR TERM...JPT SHORT TERM...Wimberley LONG TERM...Wimberley AVIATION...JPT