Area Forecast Discussion
Issued by NWS Greer, SC

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267 FXUS62 KGSP 250735 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 335 AM EDT WED MAY 25 2016 .SYNOPSIS... High pressure will prevail over the Southeast most of this week. Moist southerly flow will lead to warmer temperatures and mainly afternoon chances of showers and thunderstorms each day through Friday. A period of cooler and wetter weather may develop late in the weekend as low pressure moves onshore from the Atlantic. && .NEAR TERM /THROUGH TONIGHT/... As of 305 AM: Area of mid clouds trapped under a weak subsidence inversion will move east of the area or scatter out around daybreak. Another area of mid and high clouds will begin spreading into the mountains around that time ahead of a weak short wave moving toward the area. Southwesterly low level flow will bring increasing moisture and warmth to the area today. This will lead to weak instability across the mountains this afternoon. Isolated to scattered convection will develop across the mountains this afternoon then diminish during the evening. Forecast soundings show a capped atmosphere or very high LFC levels outside of the mountains today. The synoptic scale guidance is in good agreement on this scenario. Some of the convection allowing models show a line of convection developing to our west ahead of the aforementioned weak short wave. This convection moves into the mountains, including NE GA and the Upstate, this afternoon and dissipates as it reaches the foothills of the three states. For now, have followed the synoptic model scenario given the weak short wave and weak instability. Clouds will linger much of the night even as the convection wanes. Highs today and lows tonight will be around 5 degrees above normal. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 245 AM Wed: Generally speaking, a western Atlantic ridge will be the dominant feature over the Southeast Thursday and Friday. Moist southerly low-level flow will continue. On Thursday a broad warm front will extend from low pressure over the northern Plains southeastward into the upper Ohio Valley and vicinity, but unlike some previous runs there is no longer indication this will enhance lift over our CWFA. Diurnal destabilization will result in PoPs slightly above climo and extending to all zones. The ridge deepens by Friday afternoon and lapse rates are not quite as good, so chances are correspondingly lower then. Max temps will be slightly above climo, and mins will be several degrees above. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 310 AM Wed: The upper pattern progresses little into the weekend, with the Bermuda High holding back the central CONUS trough. While this by itself would suggest a continuation of mainly diurnal convection and near- or above-normal temps, the "wildcard" in the forecast continues to be the track of low pressure moving out of the Bahamas and toward the South Atlantic coast Saturday and beyond. Global models continue to show poor run-to-run consistency with this feature, but the latest consensus (if you can call it that) suggests the low will approach the Charleston area. Some guidance stagnates the low along the coast and eventually takes it toward the Outer Banks; the GFS and some GEM Ensemble members instead bring it onshore near the mouth of the Savannah River. While most guidance suggests deeper tropical moisture spreading over the Carolinas as the low approaches, they do so to varying degrees, and the timing thereof is not agreed upon. For now, a blend of favored guidance produces suppressed diurnal PoPs on Saturday as a pocket of dry air swings over the area ahead of the low, but then a slow but steady increase in chances from Saturday night into Monday. Max temps will fall to a couple degrees below climo early next week under mostly cloudy and damp conditions; this will keep diurnal ranges limited and thus min temps will be well above climo. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: mid clouds trapped under a subsidence inversion are spreading out across the area outside of the mountains. Expect the BKN mid clouds to scatter out near daybreak as cirrus moves in from the west. Cannot rule out some mountain valley fog, but chance will increase if the high clouds move in slower than expected. Expect cumulus to develop with heating after daybreak. Isolated to scattered mountain ridge top convection will develop through the afternoon then taper off during the evening. Confidence too low for any mention at KAVL or the other airfields. SW winds will increase in speed through the day, then taper off during the evening. Outlook: Mainly VFR conditions will prevail through the period, but patchy morning fog chances continue at KAVL. Scattered afternoon SHRA/TSRA coverage will increase Thursday through Friday - with more uncertainty on Sat. Confidence Table... 07-13Z 13-19Z 19-01Z 01-06Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the schedule TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...Wimberley NEAR TERM...RWH SHORT TERM...Wimberley LONG TERM...Wimberley AVIATION...RWH is the U.S. government's official web portal to all federal, state and local government web resources and services.