Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 240243 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1043 PM EDT Fri Oct 23 2020 .SYNOPSIS... A weak cold front will cross the area slowly on Saturday bringing a chance for widespread showers. Slightly cooler temperatures Sunday and Monday will be followed by a return to well above normal temperatures with the next round of rain possible on Thursday ahead of a strong upper low. && .NEAR TERM /THROUGH SATURDAY/... As of 1042 PM EDT Friday: Earlier shower activity over the northern foothills of NC has dissipated, so our attention has turned toward the west and a line/area of rain and thunderstorms moving east across the Cumberland Plateau. This activity appears to be on track to reach the mtns in the pre-dawn hours. Otherwise, patchy fog is likely again tonight, although may not be as widespread across mountain valleys in response to increasing cloud coverage. The warm air mass in place will support lows once again in the 50s to near 60. It now appears the a weak cold front pushing into the region Saturday will stall over the region thanks to a weak disturbance riding along the front, roughly through I-85 corridor during the day. This will help to enhance light to occasionally moderate showers over the region with sufficient instability for isolated to scattered thunderstorms from late morning though the afternoon. The clouds and rain should arrive late enough in the day for one more warm day with highs again near 80 east of the mountains. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... As of 220 PM EDT Friday: The short-term forecast picks up at 00z on Sunday with a weak, embedded upper shortwave moving over the Southeast as very broad upper trofing deepens over the Northern Rockies. For the remainder of the period, the large-scale upper pattern will continue to amplify as the above mentioned trof digs down across the Southwest and heights gradually rise over the Southeast as an upper ridge builds. At the sfc, a moist cold front will be moving thru the CWFA as the period begins late Saturday. As the front`s parent low lifts well to the north over Canada, the front will be fairly slow to move thru the fcst area with the deeper moisture associated with it lingering well into Sunday. By late Sunday, high pressure north of New England will slide farther east and a weak CAD pattern will setup. This will allow shallow moisture to persist over the area for the remainder of the period. Overall, most of the fcst area should get some decent QPF, but it`s not likely to be enough for any hydro concerns. In addition, some sfc-based instability is expected for Sunday, however it`s doubtful that any thunderstorms that do develop will become strong/severe. Otherwise, high temps will be near normal both days with lows remaining well-above normal. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 205 PM EDT Friday: The extended forecast picks up at 00z on Tuesday with deep upper trofing digging down across the extreme SW CONUS as broad upper ridging lingers over the Southeast. By mid-week, the above mentioned upper trof is expected to separate from the mean upper flow and a large cutoff low forms over New Mexico/Texas. At the same time, very broad upper trofing centered over the Great Lakes region will persist to our north. As for the remainder of the period, the long-range guidance diverges quite a bit with the fate of the closed low becoming unclear. At the sfc, weak high pressure will be lingering over the fcst area as the period begins with an elongated, nearly stationary frontal bndy to our north and west that stretches from New England to Texas. Over the next couple of days, the moist frontal bndy will slowly drift over the Carolinas as weak high pressure moves further offshore and weak, SLY return flow sets up over our area. On Thurs, the models try to move a low northward out of the Gulf of Mexico and track it over the deep south. It remains unclear how quickly this system will track north/northeastward, but it will likely bring some widespread precip and unsettled wx to our area for Thurs and Fri. Some severe wx is also a possibility with this system as the large-scale forcing appears robust. Temps will start out well-above normal on Tues and cool to below normal by the end of the period late next week. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: VFR through the end of operations this evening. Precipitation and cloudiness ahead of a cold front will reach the mtns in the pre-dawn hours, but probably not early enough to prevent fog/low stratus restrictions from developing in the mtn valleys. Confidence is not high enough to take KAVL down below MVFR at this point, though. A brief period of low clouds could also impact KCLT, but again, confidence is not high enough to indicate anything worse than a scattered cloud below 010. Wind will be light S to SW. On Saturday, an initial band of precipitation will move in from the west during the morning hours and may impact KAVL before noon. This will be handled with a PROB30. The front will slow down and lay out over the western Carolinas in the afternoon and evening. The initial band of precip is expected to weaken during midday, and then new showers and a few thunderstorms are expected to develop across the region in the afternoon. Confidence is reasonable enough to expect some precip to affect each site at some point after noon, but the timing is unclear. For that reason, we employ a PROB30 to give us a longer time range with which to indicate the associated restrictions. Chances go up Saturday evening. Expect later TAFs to refine this with TEMPO groups and prevailing restrictions as confidence in location and timing improves. Wind should stay SW. Outlook: Shower activity will continue into Sunday with occasional flight restrictions continuing through Sunday night. A brief lull might occur early in the week, but another round of precip and restrictions is expected during the middle part of the week. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 97% High 96% High 100% KHKY High 100% High 92% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 82% High 98% High 100% 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...JPT NEAR TERM...Munroe/PM SHORT TERM...JPT LONG TERM...JPT AVIATION...PM

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