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Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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319 FXUS62 KGSP 070137 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 937 PM EDT Sat Jul 6 2024 .SYNOPSIS... A weak front will move in from the north and become stationary near the southern portion of the forecast area today. This front will increase the chance for thunderstorm activity outside the mountains through Sunday. An active pattern of afternoon and evening showers and storms is expected to continue through next week. && .NEAR TERM /THROUGH SUNDAY/... As of 930 PM Saturday: At this update, convection has started to taper off with a few lingering showers/thunderstorms south of I-85 and the NC Piedmont. Instability continues to decrease, reducing storm potential. IR satellite shows shallow cloud tops over the CWA. Made some adjustments to PoPs given the current downward trend and temps with the cooler air from decaying storms. Broad longwave troughing is currently draped across much of the CONUS from the Pacific Northwest to the Ohio Valley. Stout upper ridging remains centered over California along with a second ridge that has shifted off the east coast. A few showers may linger into the overnight as southeasterly flow returns to the area and the stalled boundary slowly lifts back north into the mountains. A widespread deck of low stratus clouds is expected to develop, which will further limit any cooling in the face of moisture return. This will keep overnight lows on the mild side with upper 60s to low 70s. By tomorrow, little change is expected with regards to the synoptic pattern. Coverage of showers and storms is expected to be greater, however, given the return of rich low-level moisture and ample instability. Showers will likely develop earlier in the afternoon with storms increasing in coverage as well, especially across the escarpment and I-85 corridor. Morning cloud cover and an early start to convection will not only keep temperatures in check, but will also limit instability with surface-based CAPE progged at 2000-2500 J/kg. As with any summertime convection, isolated damaging wet microburst cannot be ruled out, especially where multicell clusters/cell mergers occur. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 145 pm Saturday: The western Carolinas and northeast GA will be stuck in a weak upper flow regime between a long wave trough centered over the central Conus, and the subtropical ridge extending from the western Atlantic into the Southeast. A deep, albeit weak SW flow will maintain very moist conditions across our area through the period, with precipitable waters expected to be above the 90th percentile of early summer climatology. With synoptic features lacking, precip chances will be strongly tied to the diurnal heating cycle, with the high moisture levels expected to result in higher-than-normal coverage of diurnal convection. PoPs for afternoon/evening showers and storms are generally 50-60% across the Piedmont, and 60-70% across the mountains for Monday and Tuesday. The main convective threats through the period will be locally excessive rainfall, as slow-moving, efficient rainfall-producing storms are expected. However, sufficient instability should be available both days to support a handful of pulse severe storms. The very moist conditions should support some degree of convective coverage (albeit diminishing) well past the typical diurnal convective cycle, likely accompanied by a small heavy/excessive rainfall threat. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 210 pm Saturday: The upper air pattern is expected to remain relatively static during the extended, with a central Conus trough expected to make only modest eastward progress, while the subtropical ridge/associated Bermuda high is forecast to strengthen across the western Atlantic. With such minimal changes in the overall patter expected, the environment over the southern Appalachians and vicinity is expected to remain more moist than is typical for early summer. This moisture could be enhanced further (albeit briefly) by the remnant circulation of T.C. Beryl, which is forecast to lift across the TN and OH Valleys during mid-week. Above-normal coverage of diurnal convection (60-70 PoPs across the mountains; 50-60 across the rest of the area) is therefore expected each day through the period. An excessive rainfall threat will continue...and may actually worsen a bit as antecedent conditions deteriorate locally. Temperatures are forecast to be within a degree or two of climo through the period. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... At KCLT and elsewhere: VFR conditions to start out the TAF period outside of areas with showers and TSRA this evening. Given the widespread coverage of TSRA east of the mountains, TEMPOS for all terminals expect mtn sites through at least 02z. VCSH are those terminals are expected after the TEMPOs expire through at least midnight. After midnight, winds will become VRB to calm at most sites. Areas that received rain this evening will be prone to FG. Confidence is medium that KCLT and KHKY will have CIGS drop into the IFR range, with KCLT in this low CIG restriction from 07z-14z. MVFR will return early morning and slowly improve to VFR by the afternoon at all sites. Another round of TSRA expected Sunday afternoon at all sites starting at 20z in the mountains and 22z elsewhere. As for the winds, again VRB to calm overnight with wind speeds starting to pick up again by mid morning, but still remaining light. Wind direction should prevail S/SE after TSRA diminishes. Outlook: A typical summertime pattern continues for most of next week, leading to showers/thunderstorms and possible restrictions each afternoon/evening. Fog or low stratus may develop each morning, especially over areas that received rain the previous day. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...JDL NEAR TERM...CP/TW SHORT TERM...JDL LONG TERM...JDL AVIATION...CP