Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
818 FXUS62 KGSP 021034 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 634 AM EDT Sat Aug 2 2025 .SYNOPSIS... Cold air damming develops this weekend, lingering into much of next week. This will allow much cooler and below normal high temperatures to return across the western Carolinas and northeast Georgia. Shower and thunderstorm chances stick around through next week but a brief lull may develop for some locations Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM EDT Saturday: Effective backdoor cold front has pushed south of the CWA, with NE surface winds observed in all locations south & east of the Blue Ridge. Weak advection of lower theta-E air along with widespread low cloud cover will result in much cooler conditions and more stable air across the area today, with max temps forecast to be 10-15 degrees below climo...or 15-20 degrees cooler than the last few days. In terms of our main climate sites...this will bring an abrupt end to a streak of 90-degrees days that began all the way back on June 21st at GSP, and on July 7th at CLT. Warmer conditions around the periphery of the CWA...especially around the Smokies and vicinity...could allow for a thunderstorm or two to develop this afternoon, but otherwise, only showers are expected, with weak upglide and E/SE upslope flow atop the stable layer being the primary sources of lift. As such, general likely PoPs are advertised across the mountains, with 30-50% chances elsewhere (even those probabilities may prove too generous across our eastern areas.) Shower chances linger into tonight, especially near the Blue Ridge escarpment, where an E/SE upslope flow is expected to persist. The lack of instability/coverage of deep precipitation cores will limit the potential for locally excessive rainfall compared to yesterday, but still can`t rule out an isolated flash flood event across the mountains this afternoon and this evening. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 100 AM EDT Saturday... Key Messages: 1) Cold Air Damming Continues through the Short Term 2) Well Below Normal High Temperatures Expected Each Day 3) Shower and Thunderstorm Chances Continue but Drier Conditions May Develop Sunday into Monday for Some Locations Abnormally strong cold air damming for this time of year remains in place through the short term thanks to a sfc high center centered over the Northeast nosing down the Appalachians. This will keep well below normal high temps, mostly cloudy skies, and rain chances around Sunday into Monday. Highs east of the mountains will range from the mid 70s to lower 80s each afternoon. Highs across the mountain valleys each afternoon will range from the upper 60s to lower 80s, with elevations above 3500 feet seeing highs from the mid 50s to upper 60s. This will lead to highs on Sunday ending up ~9-15 degrees below normal, with highs on Monday ending up ~5-12 degrees below normal. Lows each night across the mountains will range from the mid 50s to lower 60s, with lows east of the mountains each night ranging from the lower to upper 60s. This will lead to lows ending up a few degrees below normal Sunday night, becoming a few degrees below normal to near normal Monday night. As for rain chances, both global guidance and high-res guidance continue to show the potential for drier conditions to develop during the short term, mainly across the NC Piedmont and portions of the NC Foothills. Confidence on this remains very low due to continued model disagreement but the latest NBM PoPs do reflect this trend with the lowest PoPs in place over these locations. NBM thunder chances have trended down compared to this time yesterday and this makes sense given how strong the wedge is expected to be. Still could not rule out some isolated rumbles of thunder but confidence is low. No severe weather is expected thanks to the wedge limiting sfc instability. With lower PWATs through the period, any hydro concerns should remain low. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 100 AM EDT Saturday... Key Messages: 1) Cold Air Damming Lingers through the Long Term 2) A Gradual Warming Trend is expected but Highs will Remain Below Normal Each Day 3) Shower and Thunderstorm Chances Stick Around With no real mechanism available to erode the CAD wedge, it sticks around through the long term thanks to the southwestern periphery of the sfc high continuing to nose down into the region. Despite a gradual warming trend through the period, highs will remain below normal each day through the rest of the workweek. Highs on Tuesday and Wednesday will remain ~5-9 degrees below normal, becoming ~2-5 degrees below normal Thursday and Friday. Lows each night will end up near normal to a few degrees above normal. With higher PWATs returning as a frontal boundary stalls near the Carolina coast, hydro concerns may return with efficient rain rates and higher coverage of convection possible. The severe threat should remain low throughout much of the period thank to CAD and cloud cover continuing to limit sfc instability. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: NE winds of 5-10 kts and IFR cigs will continue (or soon develop where it hasn`t yet) through at least the morning hours across the Terminal Forecast Area in the wake of a backdoor cold front/responding to cold air damming development. Patchy drizzle or -RA is occurring across the area this morning, and this could expand somewhat after sunrise, possibly producing MVFR visby restrictions and perhaps a brief LIFR cig. Otherwise, gradual improvement in cigs is expected from the NE this afternoon and evening, but at least MVFR cigs are expected to persist into the evening hours. Showers remain possible through the afternoon and evening, but coverage is expected to be scattered at worst near the TAF sites...and Prob30s for SHRA are advertised at most sites at some point during the afternoon/evening. Conditions are generally expected to be too stable for thunderstorms through the period, but can`t rule out a stray TS this afternoon near KAND, although the probability remains too low for a TAF mention at this time. Cigs may slightly deteriorate tonight, mainly at the SC terminals, but MVFR is expected to generally predominate through 12Z Sunday. Outlook: Cig restrictions may linger into early Sunday across at least a part of the Terminal Forecast Area. Otherwise, the rest of the weekend looks VFR apart from the usual low stratus and/or fog each morning. Sct to numerous showers will be possible again on Sunday, especially over the mtns and western SC Upstate. A return to more typical summertime weather is expected early next week. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...AR NEAR TERM...JDL SHORT TERM...AR LONG TERM...AR AVIATION...JDL