Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
630 FXUS62 KGSP 080623 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 223 AM EDT Tue Jul 8 2025 .SYNOPSIS... Hot and humid conditions will continue thru midweek with daily afternoon and evening shower and thunderstorm chances. The heat abates somewhat going into the weekend, but daily afternoon and evening shower and thunderstorm chances continue. && .NEAR TERM /THROUGH TONIGHT/... As of 155 AM Tuesday: Mountain valley fog this morning will dissipate quickly after daybreak. Can`t rule out some patchy fog elsewhere, but chance is very low. A weak upper anti-cyclone remains over the area today but begins to weaken and move east through tonight. A lee trough develops over the area with a cold front remaining well to our north. An unstable air mass remains over the area today. Moisture pools over the mountains and east of the lee trough, but there is drying between the two. Expect diurnal convection once again with better coverage over the mountains and east tapering off to isolated coverage south of I-85. The one exception could be a differential heating boundary setting up east of I-77 which the CAMs show with better coverage developing along it. Right now, the better coverage with that feature should be to our east, but if the feature develops farther west, then coverage over the CLT Metro could be higher. SBCAPE rises to around 2000 J/kg but it`s more of a tall/skinny CAPE with high LFC`s between the mountains and differential heating boundary where drying occurs. Even where there is moisture pooling, decent DCAPE and sfc delta theta-e develops, but bulk shear is 20 kts or less limiting any potential storm organization. SPC has a Marginal risk for severe storms with damaging winds along and east of I-77. This makes sense given the afore mentioned parameters, but an isolated severe storm will be possible across the mountains as well. Highs will be in the mid to upper 90s outside of the mountains and around 90 in many mountain valleys. With dew points mixing out again during the afternoon, the heat index tops out below 105, but many locations along and south of I-85 will see values of 100 or higher. Convection diminishes and weakens during the evening and should end by midnight. Skies clear out with mountain valley fog expected. Lows will be near normal across the mountains and up to 5 degrees above normal elsewhere. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 1:45 AM EDT Tuesday: The short-term fcst picks up at 12z on Wednesday with broad upper ridging to our east and west. On Wednesday, an upper shortwave will propagate into the OH and TN valleys, resulting in height falls over our area and slightly lower thicknesses. This feature will provide some amount of upper support for our fcst area as diurnal heating produces sfc-based CAPE of 1000 to 2000 J/kg. Categorical PoPs are fcst across the mtns and NC Piedmont with likely PoPs over much of Upstate SC and the GA Piedmont. Bulk-shear values increase slightly ahead of the trof but values are not generally supportive of organized convec- tion. Nonetheless, model profiles suggests that there will be enough mid and upper-level dry air to support isolated damaging microbursts. PWs of 1.5 to 2" and fairly unidirectional low and mid-level flow will likely support cell training capable of producing isolated areas of excessive rainfall/flooding. The increased cloud cover should help keep high temperatures a few degrees cooler than Tues, though still a few degrees above-normal for mid-July. While aftn mixing is expected to lower dewpts a few degrees, heat indices will likely approach the 100 to 103 degree range over portions of the Upstate and the CLT metro area. We can expect similar unsettled weather and convective coverage for Thursday aftn and evening. Persistent SWLY low-level flow and favorable storm-motion vectors suggest a continued risk for isolated areas of excessive rainfall and localized flooding. Bulk-shear values are fcst to increase slightly, approaching 25 kts. Despite tall and skinny CAPE pro- files, a wet microburst threat will continue where the strongest updrafts can develop. High temperatures should fall a few degrees compared to Wednesday with values near climatology for mid-July. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 1:35 AM EDT Tuesday: The extended period picks up at 12z on Friday and is expected to remain fairly active thru the period. Our area will remain sandwiched between the broad, subtropical Bermuda High to our east and broad, weak high pressure to our west and north. This will keep moist, SLY to SWLY low-level flow over our area thru most of the period. Aloft, numerous weak short- waves will move across the OH and TN valleys and over the central and southern Appalachians thru the period. This energy aloft will help support likely to categorical PoPs over the mtns and foothills with chance PoPs over the Piedmont each afternoon/evening. At this time, there doesn`t appear to be a significant severe wx threat any particular day, with isolated damaging wet microbursts possible each day. With the persistent moist airmass in place, the bigger threat will likely be excessive rainfall from thunderstorms that could pro- duce localized flooding. Otherwise, high temperatures are expected to start out near-normal on Friday and gradually warm up to a cate- gory above normal by Sunday. Dewpts are expected 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 on Sunday and Monday. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: Mainly thin cirrus and light and variable winds expected through daybreak. The notable exception is mountain valley fog which has already developed in places. Guidance suggests KAVL will see restrictions, but it`s not always correct, even when conditions are favorable. Still, did go with a TEMPO for MVFR vsby and few IFR. A very unstable air mass and differential heating will lead to developing cumulus and diurnal convection, with coverage favoring the mountains. Still, there`s enough of a chance for PROB30s for all but KAND. Skies clear out overnight with the potential for mountain valley fog once again. SW wind picks up through the day, NW at KAVL, becoming light and variable overnight. Outlook: Typical summertime weather is expected into the weekend, with sct to numerous SHRA/TSRA mainly in the aftn/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