Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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310 FXUS62 KGSP 061849 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 249 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 228 PM Saturday: 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. At the surface, a weak frontal boundary has stalled across the area roughly along and just south of the I-85 corridor. This has shunted the low- level ThetaE axis and better instability/moisture east into the Midlands. Latest visible/IR satellite imagery as of this writing depicts deeper cumulus and convection scraping along our far southeast zones with a couple storms in far eastern Union (NC) county. A cumulus field is attempting to recover over north Georgia in the wake of a deck of high overcast stratus, but this attempt might be in vain with limited time left for destabilization and convective initiation. Thus, confidence in convection is highest south of I-85 through the afternoon although a couple isolated showers and storms cannot be discounted across northeast Georgia and the northern Upstate along with a stray shower or two across the mountains. Modest instability will support the potential for a couple strong storms, but severe weather potential is low owing to poor lapse rates and limited DCAPE. A few showers may linger into this evening and possibly 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 /19Z SATURDAY THROUGH THURSDAY/... At KCLT and elsewhere: VFR conditions are currently ongoing at all terminals with an afternoon cumulus field being observed, especially outside of the mountains. Afternoon showers and thunderstorms are expected generally along and south of I-85 with the highest confidence at KAND and KCLT. KGSP/KGMU are on the drier side of a weak cold front and may be just a hair too far north for convection to impact the terminals, but it would be premature to can the TEMPOs just yet. The TEMPO was dropped at KHKY, however, with the KAVL TEMPO transitioned to SHRA as confidence in convection is lowest along the I-40 corridor farther into the drier air behind the front. Heading into tonight, the front shifts back north allowing deeper moisture to return across the area and the development of a subsequent low stratus deck east of the mountains. MVFR to IFR ceilings are likely with a few instances of LIFR not out of the question. Patchy fog cannot be ruled out as well, but may end up being limited to locations that see rainfall today. Otherwise, winds will be light and variable through much of the period with north/northeast winds on the north side of the front and southerly on the south side. Outlook: An active summertime pattern will continue for most of next week, leading to scattered to numerous showers and 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...Heat Advisory until 8 PM EDT this evening for GAZ029. NC...Heat Advisory until 8 PM EDT this evening for NCZ071-072-082. SC...Heat Advisory until 8 PM EDT this evening for SCZ009-011>014- 019. && $$ SYNOPSIS...JDL NEAR TERM...TW SHORT TERM...JDL LONG TERM...JDL AVIATION...TW