Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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381 FXUS62 KGSP 250557 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 157 AM EDT Sat May 25 2024 .SYNOPSIS... Temperatures will remain above normal through the holiday weekend with a chance of afternoon and evening thunderstorms. A cold front brings another chance of showers and thunderstorms on Monday. Cooler and drier conditions move in behind the front and remain through the end of the week. && .NEAR TERM /THROUGH TODAY/... As of 143 AM EDT Saturday: A passing short wave/MCV looks like it will support the development of showers and a few thunderstorms across the foothills and western Piedmont of NC through the pre-dawn hours, so a chance was added back on this update. Think we lack sufficient leftover buoyancy to allow for anything severe, but expect plenty of lightning and some wind gusts maybe up to 40 mph in the stronger cells. Main thing is, it will probably wake a few people up if it survives to the Charlotte metro area. The rest of the forecast area should be more quiet, with mild temps through daybreak. Otherwise...areas that get rain this evening can expect some patchy fog before dawn, but that won`t last long before skies clear. Lows will fall into the mid-60s again. Another round of convection is expected tomorrow, but should be even less active than today. Weak ridging will begin to develop over the Southeast CONUS overnight, and the only supporting upper feature for convection will be an embedded shortwave that dips across the Appalachians and into the Piedmont by afternoon. CAMs suggest that a line of showers and thunderstorms will cross the area during the mid-afternoon, organized more by their supporting upper feature than by any inherent storm-scale dynamics. Sans much of an upper wave to work with, there`s pretty good consensus that deep shear will be <20kts, and so severe risk looks muted compared to today`s. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... As of 205 AM Saturday: Sunday has the potential for a few more diurnally driven convective storms as a weak shortwave moves across the area. Guidance keeps a steady stream of moisture from the SW during this time with PWATS well into the 1.5 inch range. GFS and NAM indicate modest instability during the afternoon and evening hours, supporting any initiation off the mountains. Outside of somewhat weak upper support aloft, storms that do fire have the potential to be strong to severe, with damaging winds and some hail possible. Again this will be diurnally driven and more of the typical summertime pattern the area is familiar with. Capped PoPs in the slight chance for the Piedmont and chance in the mountains. Meanwhile, an upper low forms over the southern plains and lifts NE, bringing the chance for a weak FROPA across the mountains Monday, increasing rain and TS chances once again. There is some model disagreement when it comes to the timing of the boundary and peak heating. GFS brings the FROPA into the mountains late on Monday night, which would not provide good forcing for convection. However, showers and thunderstorms are still likely given instability and daytime heating. Modeled soundings show steep sfc-3km lapse rates and modest muCAPE, but with a strong T/Td spread and inverted-V supporting strong downdrafts. By Monday night, the FROPA should slowly dissolve over the CWA and bring in a bit drier air and nip rain chances through the end of the period.Temps will remain above climo until the weak cold front when temps should cool a bit closer to normal. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 210 AM Saturday: By Tuesday, a strong ridge builds over the central CONUS, taking on an omega pattern over most of the CONUS, leaving the CWA in a weak quasi-zonal regime from the base of the trough to the north. Long range models show an upper trough dipping southward from the Great Lakes, but don`t provide much support for TS activity. There is still much uncertainty as to how far south and if the trough reaches the CWA. By Wednesday, a weak low attempts to form over eastern TX and sends a ripple in the upper flow. Possible shortwaves could traverse the area Wednesday night and bring another chance for showers/TS, but confidence is low. After Wednesday night, the ridge axis from the central CONUS propagates eastward toward the CWA and shunts rain chances with strong subsidence aloft. Dry conditions return as heights quickly rise into the end of the extended period. Temperatures should warm gradually and remain close to climo through the period as well. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Dealing with some convection moving east from the NC foothills to the western Piedmont over the next few hours, necessitating a TEMPO at KHKY and also a TEMPO at KCLT for passage of TSRA in the pre-dawn hours. The plan is for the storms to be clear of KCLT before operations really crank up this morning after 10Z. Once that is clear, would not be surprised if some fog persisted until the sun comes up and mixes it out, but will not include yet. Won`t rule out brief fog restrictions elsewhere. For the balance of Saturday, VFR with sct/bkn low clouds, and a light SW wind. Think the HRRR model has a plausible depiction of thunderstorm evolution, so this was generally followed on the timing of a PROB30 group at all terminals. The storms should die off around sunset, leaving us with convective debris clouds overnight, and possible fog restrictions in the pre-dawn Sunday. Outlook: A unsettled pattern will linger thru the rest of the weekend and into early next week, allowing for diurnal shower and thunderstorm chances each day and at least patchy fog development each night/morning. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...CP NEAR TERM...JDL/MPR/PM SHORT TERM...CP LONG TERM...CP AVIATION...PM