Area Forecast Discussion
Issued by NWS Greer, SC

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946 FXUS62 KGSP 192337 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 737 PM EDT Thu Sep 19 2024 .SYNOPSIS... The limited coverage of any showers and storms on Friday afternoon will be confined to the mountains. Meanwhile, high pressure begins to build into the region from the north and west giving our region a dry weekend. Temperatures will be above normal through the weekend then closer to normal through the middle of next week. && .NEAR TERM /THROUGH FRIDAY/... As of 545 PM: Scattered showers continue near the Blue Ridge Escarpment, generally weakening as evening cooling occurs, but with cumulus still looking vertically developed in spots particularly west of Hendersonville. Weak northerly steering flow will persist this evening and there is enough instability in the foothills to expect some isolated development south to I-85 in the Upstate and perhaps another county or so south of the current activity northeast of Asheville. Won`t rule out new development until 02-03z in our northern NC zones with weak axis of vorticity evident on water vapor imagery. Rainfall rates are expected to be too small to incur any hydro threat; lightning is proving quite isolated. Revised overnight temp and sky trends but lows would appear on track from prev fcst. Overnight temps still look to drop into the u50s across the mtns and crossover temps will likely be reached or exceeded possibly leading to the formation of dense fog across the mtn valleys and east within the adjacent foothill lowlands. A drier day is on tap for Fri with less cloud cover as deep subsidence increases from the west and hipres dominates at the sfc. There may be some limited convective activity across the mtns due to ridge top convg, but coverage of precip will be low-end due to the aforementioned subs and mlvl warming. Highs Fri will likely reach a couple cats abv normal across the forecast area. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... As of 145 PM EDT Thursday: Upper ridge will be dominating the Southern Plains as we move into the short term, with trough in place over the East Coast. With heights rising through the period, increasing subsidence will generally keep pops out of the forecast, but a weak shortwave moving down the northerly flow aloft may bring just a bit of moisture to the area briefly Saturday night, so cannot rule out some showery activity in the NW NC Piedmont. Bigger story will be the temperatures increasing through the period, with temperatures trending upwards both Saturday and Sunday, uncomfortably unseasonably warm with highs approaching mid 90s in the Upper Savannah by Sunday afternoon as the upper ridge axis pushes closer to us and the upper trough begins to lift out. Elevated dewpoints underneath the increased ridging aloft will keep overnight lows a couple of degrees above normal as well. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 200 PM EDT Thursday: The upper ridge will continue to push east as we move into the extended, eventually flattening and shifting slightly south as a mid-level low works its way out of the Rockies and across the Northern Plains. A stronger system passing across southern Canada will drag a cold front across the Great Lakes on Sunday, approaching the OH Valley late in the weekend and eventually toward the Southern Appalachians as we begin the new work week, bringing a return of pops to the mountains. Timing this far out is uncertain, and the first round of precip may dry up before the secondary round associate with the Northern Plains wave moves in Tue-Wed. High temperatures will be knocked back down closer to seasonal normals with the increasing clouds and precipitation, though increasing moisture will keep overnight lows above normal. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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At KCLT and elsewhere: A few -SHRA will persist near the Blue Ridge Escarpment in the first couple hours of the period, warranting VCSH at KAVL. Otherwise remaining cu will dissipate leaving just FEW-SCT mid cloud for most of the night, with winds remaining light. Although mixing was better today dewpoints remained at summerlike mid 60s to near 70; coupled with a slight easterly flow above the sfc, radiation fog/stratus appear likely in the mtn valleys and also near rivers in the Piedmont. Hence a period of IFR is included at KCLT/KAVL/KHKY in the morning; with lesser support from guidance and drier soils have gone no worse than MVFR at KGSP/KGMU, although trends will need to be monitored overnight. Winds pick up from the N to NE during the morning but should remain less than 6 kt. At KCLT slow improvement is expected with VFR not returning until midday. Isolated SHRA/TSRA possible in the mountains but chance too low to mention at KAVL. Winds could veer to near due E if not ESE late in the day but with speeds light and impact low, did not introduce another group to reflect shift. Outlook: No appreciable return of moisture or precip chances expected until early to middle of next week. Daybreak restrictions could recur each morning especially in mountain valleys.
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...SBK/Wimberley SHORT TERM...TDP LONG TERM...TDP AVIATION...Wimberley