Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
306 FXUS62 KGSP 171717 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 117 PM EDT Thu Jul 17 2025 .SYNOPSIS... Daily thunderstorm chances continue through the upcoming weekend. A few storms could produce damaging wind gusts and localized flash flooding. Hot and humid conditions stick around through the forecast period. && .NEAR TERM /THROUGH FRIDAY/... As of 115 PM EDT Thursday: A strong surface high remains parked over the Atlantic and the western side amplifying, keeping the flux of moisture in place. Off to the north, an area of low pressure moves out to the far NE, dragging a very weak frontal boundary toward the TN Valley. This is expected to settle over the mountains this afternoon, aiding in slightly more forcing for convective development. All other ingredients remain in place much like the past week. Guidance has PWATs in the 1.75-2.00 inch range and relatively weak steering flow aloft. For today, another round of the typical showers and thunderstorm activity starting over the mountains and eventually making its way east. CAM guidance shows more activity over the mountains with higher chances (65-85%), especially over the ridgetops. East of the mountains, PoPs drop off drastically into the slight chance (15-35%) range during the typical peak heating time frame. Any storm that can fire off has the potential to produce locally higher rain rates and an isolated/local flash flooding risk. Overnight, PoPs decrease quickly, but cannot rule out a pop-up shower or thunderstorm before midnight. For Friday, a surface high migrates east from the central CONUS along with the high over the Atlantic. In between the two highs sits the CWA, allowing for continued moisture advection and the typical diurnally driven convection chances. Again, the higher chances are over the mountains (60-80%) and elsewhere 20-40%. Temperatures remain in the low 90s today but heat up more for Friday. The heat index looks to be a bit more of an issue starting tomorrow. Many locations east of the mountains could see HI values in the 100-104 range, but remains just below Heat Advisory criteria at this time. && .SHORT TERM /FRIDAY NIGHT THROUGH MONDAY/... As of 1245 PM EDT Thursday: A fairly active pattern is expected over the weekend thru Monday, as upper ridge retrogrades slightly to the northern Gulf Coast, and heights fall across the Mid-Atlantic. This will allow a quasi-stationary front to slowly sag southward across the Ohio Valley and Mid-Atlantic. A typical hot and humid air mass in place combined with extra focus for convection near the frontal boundary will result in categorical PoPs in the NC mountains to solid chc PoPs across the I-85 corridor and southeast each day. Generally, PoPs will be the typical diurnal aftn to early evening time frame, but some increase in shear along a "ring of fire" around the upper ridge may support MCS activity making a run for the Southern Appalachians either Sunday or Monday. Confidence is still low on that. There may also be an increasing flash flood threat, as elevated PWATS in the 2-2.25" range will persist across the area thru Monday. The area of most concern will be in the NC mountains near the TN border thanks to the persistent westerly upslope flow. Another concern will be the heat index, as dewpts may not mix out as much ahead of the sagging front, while temps get into the mid 90s across most of the Piedmont. The NBM dewpts may be a tad high, but the latest forecast is for plenty of 105-109 heat indices across the lower Piedmont and the Charlotte area each aftn thru Monday. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... As of 100 PM EDT Thursday: Upper ridging begins to reassert itself from the Lower MS Valley toward the east Tuesday into Wednesday. This will allow drier air to work in from the north and bring PoPs back down closer to climo. Temps will remain above normal, but dewpts should mix out more and bring heat indices back under heat advisory criteria for most of the forecast area. && .AVIATION /17Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: Conditions for this TAF period remain mostly VFR across the terminals. TSRA chances once again for the mountain sites and KCLT this afternoon and evening. Confidence is higher across the mountains, which will keep a TEMPO going at KAVL/KHKY. A PROB30 remains in place for KCLT as the confidence is lower. TSRA should start to taper off by midnight. Overnight, there is a chance once again for low stratus or BR to form, which could drop cigs into the MVFR category and clear after sunrise. Winds today remain SW with low-end gusts possible at KCLT/KGSP/KGMU through 00z. Another round of TSRA possible Friday, mainly at the mountain sites. Will keep a PROB30 for the afternoon. Winds Friday also remain SW with a few brief low-end gusts possible at the end of the TAF period. Outlook: Thunderstorm chances each afternoon/evening. Low stratus or fog are possible each morning in mountain/river valleys. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...ARK NEAR TERM...CP SHORT TERM...ARK LONG TERM...ARK AVIATION...CP