Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 021347 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 847 AM EST Wed Dec 2 2020 .SYNOPSIS... A moderating high pressure area will be in control of our weather through Thursday. A low pressure system will cross the area this weekend. Generally fair weather expected next week. && .NEAR TERM /THROUGH TONIGHT/... As of 845 AM EST Wednesday: The latest satellite showed mostly clear skies, revealing snow cover across portions of the mountains. Ran a quick update to slow the warm up this morning. Afternoon highs may be a touch on the high side, but not enough confidence to make an adjustment at this time. Will continue to keep an eye on afternoon humidity values as there is a chance that a fire danger statement could be needed for northeast Georgia. Otherwise sfc high and shortwave ridging begin to move into the area today and slightly moderates the overall airmass. The departing trough will continue to produce gusty winds, mainly across the mountains as the backside of it continues to move over the area this morning. As the sfc high slides across the Southeast and over our region during the day, expect a shift in the winds to mainly support a west to southwesterly component. Downsloping winds will be in store with this wind shift and dry air continues to filter in through the mid-and upper-levels. With a slight breeze and the amount of dry air aloft, expect min RH values to dip below 20%, which can lead to some form of fire concerns, but shouldn`t rise to the occasion with the recent rain and mountain snow. There will be an uptick in max temperatures today as we return closer to normal for this time of the year due to increasing heights, but still remaining ~5 degrees below normal for most locations. Lows tonight will into the 20s across the cwa with a few spots slightly warmer, hovering near the freezing mark through the overnight hours. && .SHORT TERM /THURSDAY/... As of 240 AM Wednesday: Guidance coming into better agreement regarding the weather system affecting our area Friday and Saturday although some differences remain. Before then, Thursday will be dry as high pressure slides off shore. Highs will be near to slightly above normal. Change begins Thursday night as an upper low over the southern Plains begins moving east as some flavor of phasing with a northern stream short wave diving into the Great Lakes. The ECMWF shows greater phasing as the low opens up and quickly moves across the area as it is absorbed into the developing East Coast trough. The GFS keeps the low closed making it the dominant system and slowly moving it across our area. A surface low moves to near the Mobile area by Friday morning with an inverted trough to the north. Low level flow turns southerly with increasing low level moisture and isentropic lift. The guidance has generally slowed keeping most of the precip to the west Thursday night, then spreading precip over the area Friday. Forecast soundings show a warm nose developing which would mean precip would be rain, but could be a brief period of freezing rain if temps were cold enough across portions of the mountains. For now, there doesn`t appear to be a significant chance of wintry precip Thursday night/Friday morning. The surface low takes on more of a Miller B look as the low moves north along the inverted trough and strengthens Friday and Friday night. This spreads showers across the area. The ECMWF is faster showing a mainly dry Saturday as the low and associated cold front move east. The GFS is slower with showers ending Saturday morning. Both show the potential for heavy rainfall. The GFS also shows some muCAPE developing as the cold front moves through along with strong shear and helicity. Of course, there are still questions regarding these features, so flooding and severe potential remains uncertain. Both models also show a moist NW flow with CAA developing behind the departing system suggesting a period of NW flow snow. The GFS is more bullish than the ECMWF, so amounts are uncertain as well. Highs remain nearly steady Friday and Saturday. Lows will be above normal Thursday and Friday nights, then fall below normal Saturday night. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... As of 310 AM Wednesday: Forecast for the long term rather tame compared to the short term. A series of upper lows and short waves drop through the long wave trough over the eastern CONUS. Guidance differs on timing and track of these systems. The do agree that any cyclogenesis associated with these systems will generally be somewhere off shore well away from our CWFA. There is potential for some moisture to brush the mountains with elevation rain snow sometime during this period. However, timing and amounts differ completely. Therefore, have continued with a dry forecast for now. Windy to breezy conditions may also develop from time to time. Temps will remain nearly steady up to 5 degrees below normal through the period. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... At KCLT and elsewhere: VFR through the period, with the pesky cloud deck that lingered along the TN border and northern tier through the overnight hours has almost fully dissipated and should quickly scour out after sunrise. WNW winds expected generally through the morning period, with some low-end gusts still possible, especially at KAVL. Could see some wind components backing more to WSW especially across the Piedmont this afternoon, but by then wind speeds should be 5kt or below. Outlook: VFR conditions will prevail until the next system approaches the area late Thursday into Friday. Confidence Table... 13-19Z 19-01Z 01-07Z 07-12Z KCLT High 100% High 100% High 100% Low 0% KGSP High 100% High 100% High 100% Low 0% KAVL High 100% High 100% High 100% Low 0% KHKY High 100% High 100% High 100% Low 0% KGMU High 100% High 100% High 100% Low 0% KAND High 100% High 100% High 100% Low 0% 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...RWH NEAR TERM...CAC/Munroe SHORT TERM...RWH LONG TERM...RWH AVIATION...CAC

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