Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 010601 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 101 AM EST Mon Mar 1 2021 .SYNOPSIS... A cold front will cross the mountains early this morning and then cross the foothills and Piedmont through the late morning and early afternoon hours. Dry high pressure will build over from the north tonight 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 TONIGHT/... As of 1245 am EST: The latest surface analysis reveals a cold front positioned roughly from Knoxville to Chattanooga TN early this morning and making slow progress eastward toward the NC mountains. Ahead of this boundary, gusty southwest winds have developed over the higher terrain, but with max gusts likely staying just below advisory values of 45 mph along the highest ridge tops. Precipitation will begin to fill in quickly across the NC mountains as the frontal zone and associated H5 vorticity reach the spine of the southern Appalachians circa 09Z, march on to the Blue Ridge Mountains eastern escarpment by 11Z, then move east across the foothills/Piedmont through late morning. The PoP trends will follow this pattern, with categorical coverage likely at some point for most locations, but with QPF values much better along the TN border areas early this morning, and particularly across Graham and Swain Counties in the best upslope flow and longest dwelling period of the heavy rainfall. With QPF values around 1.5+ inches in these areas, minor hydro problems could arise, but this should not be sufficient for any widespread flooding and a Flash Flood Watch does not appear to be needed. Instability remains quite marginal in profiles. Will generally keep thunder out of the forecast, but an isolated rumble cannot be completely ruled out with the fropa. Temperature trends will be hard to pin down today, with falling temps likely in the cold advection across the mountains, steady temperatures across the northern tier in balanced cold advection but warming post-fropa downslope flow, and a modest afternoon bump in temps in the western Upstate and NE GA. Gusty northwest winds will also develop in the cold advection through the day, but with gust values again below advisory criteria in the windiest mountain locations where a secondary, reinforcing cold fropa arrives this afternooon. A trailing but vigorous shortwave will reach the mountains again by late day. However, the deeper moisture should settle generally southeast of our Piedmont counties by sundown along with the passing cold front. Any shallow upslope moisture into the western mountains will dry up fairly quickly in the cold air along the spine of the mountains this evening. So, any isolated snow showers or flurries will be short-lived and non-accumulating. 1032 mb surface high pressure will then build over the OH River valley tonight, with chilly thicknesses spilling southward east of the Appalachians. && .SHORT TERM /TUESDAY 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 asscoiated 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 /06Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Anticipate mainly thickening and lowering VFR ceilings early this morning as a cold front and associated deeper moisture moves in from the west. The narrow band of frontal moisture should provide MVFR to lower end VFR cigs during the passsage of the main bands of rain showers with the front, generally from just before daybreak west to mid-morning east. VFR cigs will then lift and scatter through the afternoon hours, with just FEW to SCT high clouds tonight as drier high pressure builds in from the north. Gusty southwest flow this morning will become slightly gustier W to NW flow this afternoon following fropa and the onset of cold advection. Most locations lose the gusts by early evening, but KAVL will be the exception with continued NW gusts into the 20s through 06Z Tuesday. Outlook: VFR conditions briefly persist into Tuesday under dry high pressure. However, moisture may surge back into the area by Tuesday, with restrictions and precipitation chances returning through early Wednesday. Another round of drying is expected by late Wednesday, likely continuing through the end of the work week. Confidence Table... 06-12Z 12-18Z 18-24Z 00-06Z KCLT High 100% High 95% High 100% High 100% KGSP High 95% High 93% High 100% High 100% KAVL High 85% High 96% High 99% High 100% KHKY High 99% High 100% High 100% High 100% KGMU High 95% High 96% High 100% High 100% KAND High 97% High 94% High 100% 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: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...HG NEAR TERM...HG SHORT TERM...CSH LONG TERM...CSH AVIATION...HG is the U.S. government's official web portal to all federal, state and local government web resources and services.