Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
604 FXUS62 KGSP 181904 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 304 PM EDT Sat Jul 18 2026 .WHAT HAS CHANGED... Temperatures have trended slightly cooler late next week. && .KEY MESSAGES... 1. Hot and humid conditions will linger thru Sunday with heat index values ranging from 100 to 106 degrees each afternoon. Slightly cooler temperatures return next week which should keep heat indices mostly below 105 degrees. 2. Coverage of mainly diurnal showers and thunderstorms increases thru Sunday. A few severe storms are expected today and Sunday, with damaging winds likely to be the main hazard. Mainly diurnal shower and thunderstorm chances linger through Tuesday, before a cold front brings potentially more severe weather on Wednesday. && .DISCUSSION... Key message 1: Hot and humid conditions will linger thru Sunday with heat index values ranging from 100 to 106 degrees each afternoon. Slightly cooler temperatures return next week which should keep heat indices mostly below 105 degrees. Better convective coverage and associated cloud debris, along with lower thickness values, should allow for slightly cooler temperatures this weekend ranging from the low to mid 90s outside the mountains. However, dewpts will likely remain higher, ranging from the low to mid 70s. This will allow hot and humid conditions to linger thru the weekend with triple digit heat indices expected each afternoon outside of the mtns. Union County, NC is still expected to be the only county in our fcst area with significant coverage of 105 heat index values today. Isolated locations elsewhere could briefly see values of 105. Temperatures on Sunday should be a degree or 2 cooler which should keep any heat index values of 105 more isolated. Individuals should prepare for elevated heat thru the weekend. Stay hydrated, take frequent breaks in air-conditioned or shaded areas, and never leave children or pets unattended in vehicles. Key message 2: Coverage of mainly diurnal showers and thunderstorms increases thru Sunday. A few severe storms are expected today and Sunday, with damaging winds likely to be the main hazard. Mainly diurnal shower and thunderstorm chances linger through Tuesday, before a cold front brings potentially more severe weather on Wednesday. An upper trof will dig into the Great Lakes region and the north- eastern CONUS thru Sunday as a cold front lays over the Carolinas from the north. Increased moisture advection ahead of the front and increasing low-level convergence will support an increase in convec- tive coverage both days. With sfc-based CAPE likely reaching 2000 to 3000 J/kg during peak heating and deep layer shear increasing to 15 to 25 kts each day, convection will likely become more organized. Steep low-level lapse rates and high precip water values will create a threat for strong/damaging downbursts. As such, the current SPC Convective Outlooks showing Marginal and/or Slight risk areas across our fcst area for both days appear warranted. Diurnal convective chances linger thru Monday but confidence on the severe threat remains lower at this time. We should see a brief lull in coverage on Tuesday before a cold front brings better coverage back on Wednesday. Strong to severe storms will likely be possible on Wednesday, but confidence wrt timing and extent this far out remains low. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... At KCLT and elsewhere: Sct convection has developed over the NC mtns during the past few hrs, and is expected to gradually spread eastward thru the afternoon and into the evening. To account for this, I have VCSH with PROB30s for TSRA at KCLT and the Upstate terminals. I have TEMPOs for TSRA at KAVL and KHKY as they will likely have more coverage in their vicinity. Otherwise, activity should diminish and move east of our fcst area later this evening. Another round of mtn valley fog/stratus is likely overnight, but I`m not confident enough that it will reach KAVL to include any restrictions in the TAF. Tomorrow should be similar to today, with sct convection initiating over the higher terrain and spreading east/south as the day wears on. Outside of the mtns, winds will remain SWLY thru the evening with some low-end gusts at the Upstate terminals and KCLT. They will go light and VRB to calm later tonight and pick back up from the SW tomorrow afternoon. Outlook: Good coverage of afternoon/evening SHRA/TSRA continues thru Monday with less coverage expected on Tuesday before increasing again on Wednesday. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Heat Advisory until 8 PM EDT this evening for NCZ082. SC...None. && $$ JPT