Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 281934 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 234 PM EST Sun Feb 28 2021 .SYNOPSIS... A cold front will cross Tennessee tonight then cross our area by mid day Monday. Dry high pressure will build over from the north as the high center moves from the Great Lakes to the Mid- Atlantic coast Monday night into Tuesday. Unsettled weather returns from the west Tuesday night into Wednesday morning. Another low pressure system may affect the Gulf Coast region Friday into Saturday. && .NEAR TERM /THROUGH MONDAY/... As of 205 pm: Warm sector air mass is now firmly in place across the forecast area, with gusty SW winds and increasing insolation having allowed for a rapid warm-up...by as much as 15 degrees in just a couple of hours...after the cool start beneath earlier fog/low stratus. Spotty shower activity is noted across the great valley of East TN, and some of this will probably develop into SW into the evening on the strength of mechanical lift. May also still see some showers pop in the lower/eastern SC Piedmont, where weak sbCAPE is developing. Otherwise, potent short wave trough/upper low will dig from the Canadian prairie this afternoon to the northeast Conus by the end of the period, allowing a fairly strong frontal zone to move across the TN and OH Valleys late this afternoon into the evening. A frontal band of convection is forecast to fill in across this region during the evening, as the front encounters moderate instability. In fact, the frontal band should be quite vigorous as it approaches the southern Appalachians late tonight, and the NC mountains are where the highest rainfall totals are expected across our forecast area through the period, with 1-2 inches appearing likely across the Smokies and vicinity. However, with meager-at-best instability expected across our area and lackluster upper air support, to go along with the typical high terrain disruption of the frontal circulation/low level convergence, the intensity and coverage of the frontal band is forecast to diminish as it moves across the forecast area Monday morning. As such, the threat of severe convection should remain west of the area, while any low end excessive rainfall threat will remain confined to extreme southwest NC. Despite the expected diminishing trend in the frontal band, it should hold together long enough to support categorical pops across the entire area during the morning. Precip should be all but done by mid-Monday afternoon. Other than a brief period this evening, gusty SW winds are expected across much of the area into Monday morning, before gusty NW winds develop behind the front late morning into the afternoon. Min temps will be very warm tonight, and daily record warm lows...which are generally around 60 at the main climate sites...will be in jeopardy. After the very warm start Monday, developing cold advection will limit the diurnal heating potential, and only modest warming is expected across the mtn valleys and Piedmont/foothills, while temps will slowly fall throughout the day across the high elevations. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 1205 pm EST Sunday: As sfc ridging rolls over into the region Monday night, the llvls will continue to dry, but model cross sections depict varying degrees of mid and upper level moisture lingering within the west to wsw flow aloft. Gridded model sky cover solutions are all over the place, and at this point, the generic partly cloudy should cover it. Downstream of developing southern stream low pressure, clouds should thicken again as Tuesday wears on and within the cool NE llvl flow, maximum temperatures will be back to below climo values. From late day Tuesday into Wednesday morning, as forcing and better moisture associated with the encroaching southern stream system overspreads the region, pcpn will be become widespread. Vertical temperature/moisture fcst profiles over the NC mtns still suggest that a period of snow developing into a wintry mix remains possible during this time. Fast moving s/wv passage is expected on Wednesday, the axis of which is timed to be near the coast by the afternoon. Whatever the orientation and cvrg of pcpn shield is in the morning should be replaced by dry slotting by Wed afternoon. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 1215 pm EST Sunday: No change to the going dry and mild fcst for Thursday as extended range guidance remains in good agreement in progging deep layered dry air within the cyclonic flow aloft and a dry northerly llvl flow. Within the lingering llvl northerly flow, a dry cold front is progged drop south through the region on Friday ushering in another period of below climo temperatures. The mean pattern does not change very much for next weekend, featuring a lingering eastern CONUS trough. Forcing rounding the base of upper trough is progged to activate baroclinic zone, but way off to our south and into the offshore Atlantic on Saturday into Sunday. The dry conditions will continue with temperatures around 5 deg F below the early March climo each day. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... At KCLT and elsewhere: Lingering low cloud cover is scattering/ clearing early this afternoon and visby is (finally) improving quickly in the KCLT area. VFR conditions should be seen at all sites no later than 20Z. Most terminals will see gusty S/SW winds this afternoon that will likely diminish a bit this evening. However, SW winds should begin to pick up again after midnight as surface gradient increases in advance of an approaching cold front. Can`t rule out a brief return of fog btw roughly 03-06Z. However, fog chances will decrease once winds pick up late tonight. Cigs should lower to MVFR after midnight as rain chances also increase. Most sites will see categorical SHRA for several hours from around daybreak through the morning. Improving conditions are expected at KCLT during the 18Z-00Z Monday outlook period, with NW winds developing in the wake of the front. Outlook: Drier high pressure building back into the area late Monday will result in improving flt conditions through early Tuesday. Moisture will then surge back into the area by the end of the day Tuesday, with restrictions and precipitation chances returning Tue night into early Wed. Another round of drying is expected by late Wed, likely continuing through the end of the work week. Confidence Table... 19-01Z 01-07Z 07-13Z 13-18Z KCLT High 98% High 100% High 90% High 96% KGSP High 89% High 100% High 96% High 92% KAVL High 100% High 96% High 83% High 92% KHKY High 92% High 95% Med 68% High 92% KGMU High 92% High 99% High 97% High 91% KAND High 93% High 100% High 94% High 91% 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...HG NEAR TERM...JDL SHORT TERM...CSH LONG TERM...CSH AVIATION...JDL

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