Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 271803 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 103 PM EST Sat Feb 27 2021 .SYNOPSIS... A front stalled south of our region will gradually lift northward as a warm front through Sunday. A cold front will approach the southern Appalachians from the northwest Sunday night and cross the area on Monday. Dry high pressure moves from the Great Lakes to the mid Atlantic coast Monday night into Tuesday before unsettled weather returns from the west Tuesday night into Wednesday. A stronger storm system could arrive by Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 100 PM: The CWA remains under a decaying CAD setup, with parent high already well off the East Coast and continuing to distance itself from our area, and low-level winds veering such that low-level upglide is pretty much history. That said, strong inversion is expected to limit mixing, and cloud cover looks pretty stubborn this aftn. Still retaining plentiful low clouds thru the aftn, and brought max T values down. However, any insolation will lead temps to rebound rapidly wherever breaks/scattering do occur; warmest airport site in the CWA is Franklin with temp of 68; still in the 40s at the sites where the low cigs have not managed to budge at all. Think many of those areas will see enough lifting/scattering to allow temps in the mid-50s at least by mid-aftn. The sub-trop ridge becomes the dominant feature thru the rest of the period as a warm/stat front develops just to the NW of the area. Have maintained low-end chance PoPs across the NC mtns this afternoon and thru the overnight within continued moist mech lift; the previous fcst values from early morning still look good. Pockets of h5 vort energy will traverse the aforementioned frontal zone today and enhance the convective potential. By the afternoon/evening general thunderstorms are possible along the nrn TN/NC spine, with most of this activity developing on the TN side, however, a couple tstms are possible across the nrn NC mtns as well. With increasing llvl GOM moisture and stratus likely developing overnight, expect mins to be held quite a bit abv normal with readings generally in the 50s over most locales. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 230 am EST Saturday: Deep layer southwesterly flow will continue over the southeastern U.S. on Sunday, with a split flow pattern developing back over the western and central CONUS. Meanwhile, deeper moisture will remain wrapped north and west of our area through the day on Sunday along a stalled frontal boundary. The southwest flow and associated warming of 850 mb temps will permit maxes to run well into the 70s for many areas Sunday afternoon, with PoPs for showers generally confined to northern and western sections. The more progressive northern stream will send shortwave energy into the lower Ohio Valley Sunday night, while the southern stream develops into a cutoff low over west Texas. The northern stream trough will cross the southern Appalachians Monday and push a cold front through the region. The deepest moisture and forcing ahead of the sagging cold front will occur late Sunday night into Monday morning, with drying from the northwest Monday afternoon. QPF amounts are down slightly given the better forward movement of the boundary on recent model runs. Instability with the fropa will be modest as well, so neither hydro nor severe appear to be prominent concerns - although a heavy rain mention will be continued in the mountains in the HWO for very isolated, minor flooding late Sunday night. Right entrance region upper jet divergence will cross the area late Monday post fropa, however, deep-layer drying will have developed by then and dry profiles continue through Monday night in the northwesterly flow. The only exception will be very shallow northwest flow moisture in the NC mountains Monday night, but any brief snow shower or snow flurry activity looks quite isolated at best along the spine of the northern mountains. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 230 am EST Saturday: Disparate solutions exist among the models in the Tuesday timeframe with regards to the handling of the southern stream low/trough evolution eastward from the southern plains to the lower MS River Valley. The ECMWF has considerably more forcing and associated moisture through mid week, with the GFS drier. Will keep a chance PoP mention in the forecast for Tuesday night and Wednesday at present during the best consensus period. Given the strength of the high to the north, and chilly thicknesses in place on Tuesday, there is some potential for mixed mountain/nrn tier ptypes at onset Tuesday night. The passing upper energy will move east of the area on Thursday, with a relative lull in the forecast expected. The next robust southern stream system may begin to approach the Deep South on Friday. Anticipate moisture spilling back into the region from the west ahead of this system Thursday night through Friday, but again with considerable model uncertainty. Will focus the best chance PoPs for showers on Friday. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... At KCLT and elsewhere: Low stratus/stratocu deck associated with decaying CAD regime will make for a tricky forecast this aftn at all sites except KAVL. The initially widespread LIFR deck has begun to scatter/lift in some spots but has remained essentially unchanged since daybreak elsewhere. LAMP guidance is having trouble keeping up with the trends, it seems. Have leaned pessimistic in the first few hrs, but gradual improvement does look likely this aftn across the SC sites and KCLT. Erosion of the deck should allow VFR to persist into evening. A weak front will stall across the area late today, being reactivated as a warm front tonight by low pressure over the mid-MS Valley. Combined with a moist PBL, that looks likely to bring back IFR-LIFR cigs and fog (possibly dense) by early morning to most of the area. This likely won`t scatter/lift until nearly midday Sunday. Winds will be fairly light and mainly southwesterly today/tonight; gusts will develop Sunday, especially following the erosion of the low clouds, with deep mixing in the presence of fairly strong midlevel winds in the warm sector of the aforementioned low. Precip chances are too low to mention this period. Outlook: Flight restrictions and chances for precip are expected to return Sunday and linger into early next week. Drier hipres will build back into the area by Tuesday. Confidence Table... 18-24Z 00-06Z 06-12Z 12-18Z KCLT High 83% High 90% Med 61% Med 70% KGSP High 87% High 95% Med 75% Med 78% KAVL Med 73% High 96% High 88% High 95% KHKY Med 78% Med 76% Med 62% Med 65% KGMU High 87% High 95% High 82% High 80% KAND High 84% High 95% High 87% High 86% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...SBK/Wimberley SHORT TERM...HG LONG TERM...HG AVIATION...Wimberley

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