Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 271130 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 630 AM EST Sat Feb 27 2021 .SYNOPSIS... A front stalled south of the region today 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 will build over from the north 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/...
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630 AM Update...The sfc wedge continues to weaken and become less defined this morning. Not seeing any dense fog outside of the lower NC mtn valleys, but there could be isol pockets of 1/2 SM or less VSBY over the next few hrs mainly across the I-40 corridor. Low clouds will hang tough and slowly lift thru the late morning. 400 AM Update...Isolated td/s are running a little lower than fcst/d and have adj up in the grids. This leaves most locales with low tdd/s, generally 0-3 F across the FA. The lowest vsby is occurring along and north of I-40 and will continue to monitor this area for possible dense fog formation as sfc wedge becomes more shallow thru daybreak. Low stCu and periods of light rain will continue across the FA this morning and keep conds fairly steady state thru mid morning as a sfc wedge begins to break down. Not anticipating a widespread dense fg threat due to lack of rad cooling, but sfc tdd/s are running pretty low across the nrn zones and will monitor thru for any possible products, esp as the wedge weakens and lifts north arnd daybreak. The sub-trop becomes the dominate feature thru the rest of the period as a warm/stat front develops just to the NW of the area. Will maintain low-end chance PoPs across the NC mtns this afternoon and thru the overnight within continued moist mech lift. Pockets of h5 vort energy will traverse the aforementioned frontal zone today and enhance the convective potential. By the afternoon/evening general thunderstorms look probable along the nrn TN/NC spine, with most of this activity developing on the TN side, however, a few tstms are possible across the nrn NC mtns as well. Max temps will rebound today as the sfc flow becomes sw/ly associated the strengthening sub-trop ridge and will expect highs arnd 70 F over the srn zones and low to mid 60s north where cloud cover will hang on longer. 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.
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&& .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 /12Z SATURDAY THROUGH WEDNESDAY/...
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At KCLT and elsewhere: Low-end flight cats will continue or develop this morning across all TAF sites as a shallow sfc wedge begins to weaken and moisture levels remain high. Expect KCLT to remain IFR/LIFR thru late morning and introduced a TEMPO VLIFR aft 08z with light rain affecting the area and likely lowering CIGs. Conds improve slowly by the afternoon, with most sites going VFR, as hipres works across the OH Valley and mixes in llvl dry air. Northeasterly winds will switch to a sw/ly direction by mid morning as the sfc wedge continues to breakdown and the synoptic pattern favors an Atl ridge axis. A return of llvl moisture overnight will generate IFR/LIFR CIGs aft 09z or so thru the morning hrs. Outlook: Scattered to numerous showers with associated flight restrictions are expected to return Sunday and linger into early next week. Drier hipres will build back into the area by Tuesday. Confidence Table... 11-17Z 17-23Z 23-05Z 05-06Z KCLT High 89% Med 75% High 95% High 100% KGSP High 89% High 95% High 100% High 100% KAVL High 83% High 80% High 100% High 100% KHKY High 83% Med 75% Med 75% Med 66% KGMU High 89% High 80% Med 70% High 100% KAND High 89% High 80% High 90% High 94% 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
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...SBK SHORT TERM...HG LONG TERM...HG AVIATION...SBK

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