Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
136 FXUS62 KGSP 090612 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 212 AM EDT Wed Jul 9 2025 .SYNOPSIS... Hot and humid conditions will cool closer to normal late this week with numerous afternoon and evening showers and thunder- storms expected each day. Temperatures increase again over the weekend and early next week as an upper ridge amplifies. Diurnal showers and thunderstorms will continue each day. && .NEAR TERM /THROUGH TONIGHT/... As of 210 AM Wednesday: Mainly cirrus with some patchy stratocu early this morning shouldn`t be enough to limit another round of mountain valley fog. Patchy fog possible elsewhere. Fog should dissipate relatively shortly after daybreak. Overall a much better chance of convection today with a moist, unstable air mass over the area. Dewpoints will mix out somewhat this afternoon, but not nearly to the extent of yesterday. This will lead to SBCAPE in the 2000 J/kg range. Weak height falls are expected as a short wave approaches the area. Surface forcing will be improved by an old outflow boundary moving in from the west. With less mixing, LFC`s will be lower leading to thicker CAPE profiles than the last few days despite meager lapse rates. Bulk shear romaines 20 kts or less, with higher values north of our area. DCAPE and sfc delta thet-e values are also lower than the past few days due to deeper moisture, but they won`t be eliminated. CAMs are in general agreement of convection initiating over the mountains and moving south and east across the area. A consolidating cold pool could help storms become semi-organized as they cross the area. All of this to say severe thunderstorms are possible with damaging winds in wet microbursts the main threat. That said, there is some large hail potential as well given the thicker CAPE profiles. Guidance is also consistent on better heavy rain potential to our east; however, with the high PW values and somewhat organized convection, there will be an isolated flash flood threat. Some of the CAMs show merging convection from the mountains and convection moving NE along the sea breeze which moves well inland from the coast. This could slow convection down and potentially lead to some training cells. Given the uncertainty of timing and location of this potential, will hold off on any watches at this time. Highs will be few degrees above normal today, so even with less dewpoint mixing, heat index values remain below 105. Convection lingers into the evening then dissipates or moves east of the area around midnight. Mountain valley fog is expected once again, and areas of low clouds and fog will be more likely elsewhere. Lows will be near to slightly above normal. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 1:25 AM EDT Wednesday: The short-term fcst picks up at 12z on Thursday with broad upper ridging to our east and west. The large- scale upper pattern won`t change much thru the period, with numerous weak upper impulses translating over our area on Thursday and Friday. At the sfc, we will remain under the western periphery of the Bermuda High. This will keep moist, SWLY, low-lvl flow over our area thru the period. We can expect active weather each day with sct to numerous showers and thunderstorms each afternoon and evening. The persistent SWLY low-level flow and favorable storm-motion vectors suggest a con- tinued risk for isolated areas of excessive rainfall and localized flooding each day. Model profiles continue to support some strong to severe storms each day as well. High temperatures on Thursday should remain near-normal with highs topping out a few degrees above-normal on Friday. Heat indices should remain below Advisory criteria thru the period. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 1:15 AM EDT Wednesday: The extended period picks up at 12z on Saturday and is expected to remain active thru the period. Our area will remain on the western periphery of the broad, subtropical Bermuda High and broad, weak high pressure to our west and north. A couple of low pressure systems will lift up and over the Great Lakes region thru the period, but any frontal boundaries associated with these systems are expected to wash out/dissipate as they approach our area. Our area will remain under moist, SWLY low-level flow thru the weekend. Early next week, low-level winds could take on a weak NLY component, but they will likely be light and vrb for much of the time. Aloft, numerous weak shortwaves will move across the OH and TN valleys and over the central and southern Appalachians over the weekend and early next week. This energy aloft will help support above-climo PoPs over the mtns and near- climo PoPs outside the mtns each afternoon/evening. Towards the end of the period, diurnal PoPs increase to likely across most of our CWA. At this time, there doesn`t appear to be a significant severe wx threat any particular day, with isolated strong to severe thunderstorms possible each day. With the persistent moist airmass in place, the bigger threat will likely be excessive rainfall from thunderstorms that could produce localized flooding. Otherwise, high temperatures are expected to remain about a category above normal thru most of the period. Dewpts are fcst to remain low enough to keep heat indices below Heat Advisory criteria, although some values between 100 and 105 degrees are possible over our southern Upstate and Piedmont zones each day. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: Mainly cirrus with some stratocu to start early this morning. Expect another round of mountain valley fog dissipating after daybreak. Patchy fog possible elsewhere with KHKY having the better chance, but not high enough for the TAF at this time. A better chance of convection today with a moist, unstable air mass and boundary interaction. Have gone with a mix of VCTS, TEMPO, and PROB30 to indicated the best times for convective coverage. Some of the convection could linger later into the evening or early overnight, but left out for now due to TAF rules. Low clouds and fog may be more likely across the area late tonight. Light S to SW wind this morning, picks up speed during the day, then turns NW behind the convection. There will be some potential for strong thunderstorm outflows, so expect variable flight conditions and strong gusts near storms. Outlook: Typical summertime weather is expected into the weekend, with scattered to numerous thunderstorms mainly in the afternoon/evening and fog and/or low stratus possible each morning. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...JPT NEAR TERM...RWH SHORT TERM...JPT LONG TERM...JPT AVIATION...RWH