Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 251428 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1028 AM EDT Sat Mar 25 2017 .SYNOPSIS... Moisture will gradually return to the region today around offshore Atlantic high pressure. Meanwhile, a low pressure system will lift from the southern plains to the Midwest and push a band of moisture toward the southern Appalachians. Deep moisture and persistent southwesterly flow will set up over the southeast Sunday through Tuesday with several rounds of showers and thunderstorms likely. Drier air should return by the middle of next week. && .NEAR TERM /THROUGH TONIGHT/...
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1015 AM EDT cover has dissipated a fair amount over portions of the CWFA with sct stratus and cirrus steadily streaming across the region. With the persistent SLY low-lvl flow, sky cover should remain sct to bkn over most of the area over the next several hours. Still expecting precip to hold off until later this evening with widespread coverage not likely until tomorrow morning. Otherwise, an ulvl ridge axis will slowly shift east of the area thru the period as h5 heights begin to fall across the wrn zones. An active occluded system has developed across the srn Plains and this will track to the NE...reaching the Midwest by 12z Sun. Meanwhile...good difl flow aloft will engulf the FA and continue transporting thick Ci over the area. There is some measure of llvl Atl/GOM rounding a sfc ridge into the wrn zones and this will keep low clouds across the mtns for much of the day. Most sites will experience few/sct low clouds by the afternoon along with the prevailing Ci. Not expecting much chance for precip until the better dynamical forcing reaches the mtns and combines with llvl mech lift. Sometime aft 03z still looks favorable for the onset of -shra...which will increase in coverage north and east thru 12z. With little instability and h5 vort energy remaining streamlined...a strong subs inversion at h7 will not be overcome leading to relatively shallow shower activity with no good chance of thunder. Qpf amounts will thus be on the light side with the favored srn Transylvania and srn Jackson counties receiving arnd 3/4 to 1 inch thru 12z. Max temps today will likely reach a cat or so above normal as ssw/ly flow continues. Mins will be held about 8-10 degrees above normal in good cloud cover and continued llvl mixing.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 230 AM EDT Saturday: A negatively tilted upper trough will stretch from the Midwest to the southern Appalachians on Sunday morning, with all of the best associated upper forcing quickly lifting northeast of the region through the day. However, a persistent moist southwesterly fetch will continue across the area Sunday through Sunday night. Thunderstorms will be possible throughout the region, but the best instability should be draped across locations southeast of I-85 Sunday afternoon. 40 kt of deep layer shear will be in place Sunday, but with warm and moist profiles limiting instability and the associated severe weather potential. Another upstream system will move from the plains to the Midwest Sunday night through Monday, with the trough axis lifting across our region Monday night. Fairly steep mid level lapse rates of 6.5 to 7 degrees C/km are expected late Monday into Monday night. SBCAPE values are likely to peak in the 1500 to 2000 J/kg range late Monday afternoon as dewpoints in the mid 50s or better persist while maximum temperatures recover into the middle 70s in many locations. Bulk shear values should be about half of what they were Sunday, but with decent thermodynamics and stronger upper DPVA/jet divergence forcing during peak heating. These ingredients may lead to isolated severe thunderstorms Monday afternoon and evening. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 245 AM EDT Saturday: Surface low pressure passing north of the forecast area on Tuesday will keep the southeast in a moist southwesterly fetch through the day. There is some measure of uncertainty over how quickly the passing upper trough will depart east of the area, but chances look decent that some measure of forcing will continue across eastern piedmont sections through mid day on Tuesday. The best lingering thunderstorm chances will be generally along and east of I-77. The trailing weak cold front will then settle into the region from the northwest Tuesday night, and possibly move just south of the area on Wednesday to bring in drier air. Southeast ridging will continue through Wednesday night as another closed low pressure system moves slowly eastward across west Texas. The upper ridge will start to break down on Thursday, but the timing of this remains somewhat uncertain given the spread in the handling of the upstream system as it gradually opens up and phases back in through late week. Nevertheless, a period of unsettled weather should redevelop Thursday through Friday as moist southerly return flow develops atop surface high pressure in a favorable location for weak cold air damming. Confidence on the timing and placement of PoPs, QPF, and instability for thunder is rather low given the spread among the faster GFS/GEFS and the slower ECMWF. Will trend the forecast cloudier late week with a return of chance PoPs for showers as moist upglide gets reeastablished. Will feature slightly cooler temps by Friday with weak cold air damming possible - at least across the northern tier. Will follow the blended WPC solution that leans toward the slower timing. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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At KCLT: Upper level clouds will dominate thru most of the period. Some VFR clouds will develop this afternoon...then VFR CIGS likely aft 06z. Slow moving pre-frontal showers will develop to the west late...but the terminal shud remain dry with lowering CIGS into the MVFR range aft 10z. Elsewhere: VFR conds this morning and afternoon at all sites except KAVL where morning MVFR stcu will persist thru mid-morning. A pre-frontal band of -shra will move into the mtns late and likely reach KAVL arnd 02z. This area of precip will gradually shift east thru the later period, warranting prob30s and prevailing -shra while lowering flight conds into the MVR/IFR range. Outlook: Areas of precip will continue Sunday likely creating flight restrictions across all terminals. An unsettled and moist pattern will persist next week and maintain the chances for low CIGS and VSBY. Confidence Table... 14-20Z 20-02Z 02-08Z 08-12Z KCLT High 100% High 100% High 100% Med 76% KGSP High 100% High 100% High 100% Med 75% KAVL High 100% High 100% High 95% Med 79% KHKY High 100% High 100% High 88% High 88% KGMU High 100% High 100% High 100% Med 74% KAND Med 76% High 100% High 100% High 82% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link:
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...JPT SHORT TERM...HG LONG TERM...HG AVIATION...JPT/SBK is the U.S. government's official web portal to all federal, state and local government web resources and services.