Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 270116 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 816 PM EST Fri Feb 26 2021 .SYNOPSIS... A front will remain stalled south of the region into Saturday as high pressure remains to the north. Gulf moisture will continue flowing north over the front through tonight. The boundary will retreat northward as a warm front through Sunday, with warmer temperatures gradually returning. Another cold front will cross the area from the northwest Sunday night through Monday with abundant moisture. Brief drying is expected Monday night into Tuesday before unsettled weather likely returns to the region through the middle of the week. && .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 700 PM Friday: Rain is still ongoing across much of the cwa, with parts of the southern tier gradually drying out. Wet Bulb temperatures at the sfc are just above 32 F in Avery County, but with multiple reports of snow, sleet, and freezing rain across Watauga and Ashe Counties, I`ve decided to hold on to the Advisory and let it expire at it`s original end time. With the sfc high hovering off the New England coastline, the wedge is still holding strong across the cwa with winds steadily coming out of the N and NE. 850 mb winds are steadily coming out of the S to SW at around 40 kts, which is allowing the wedge to hold on strong. Eventually, the wedge will erode with a warm front expected to lift across the area overnight into early Saturday, which allows winds to veer to the S and SW tomorrow. This will set the area under the warm sector and thus, temperatures will rise 10+ degrees compared to today for Max T`s on Saturday. The southern stream energy aloft will lift to the north with the sfc low riding underneath and will lead to a much drier day tomorrow compared to today. Cloud cover should remain strong, but a few peaks of sunshine can`t be ruled out during the day Saturday. Some lingering upslope showers could persist across the southern mountains and adjacent foothills on Saturday, but should remain mostly dry outside of those locations. Temperatures will remain above-normal for tonight as we stay socked in under cloudy skies, but should slowly rise during the overnight period due to the approaching warm front and eventual fropa. Tomorrow will remain above normal as most locations will end up in the 60s and 70s across the entire cwa for Max T`s tomorrow. && .SHORT TERM /SUNDAY THROUGH MONDAY/... As of 200 pm Friday: The upper air pattern will remain more or less steady-state through the first half of the short term, with ridging persisting off the East Coast and a trough over the interior West, before a complex split flow pattern evolves late in the period. For our forecast area, this means deep SW flow will persist though much of the period, with a warm sector regime yielding well-above normal temps (maxes 10-15 degrees above climo, mins 15-20 degrees above), nocturnal low clouds, and low end shower chances. By Monday, a potent northern stream short wave trough will progress across southeast Canada and the northeast Conus, allowing frontal boundary to sag into the CWA, bringing likely to categorical probabilities of rain from late Sunday night into Monday morning. The latest guidance is in general agreement in depicting a well-forced frontal zones into the TN Valley and southern Appalachians which becomes less so as it sags southeast into the Piedmont. Meanwhile, short term guidance depicts barely >0 values of CAPE in the warm sector. As such, current indications are that any heavy rainfall potential will likely be confined to the NC mountains, while the severe wx threat appears minimal in light of decreasing forcing/unfavorable frontal orientation, very low instability and less than ideal shear parameters given the meager buoyancy. The front will likely sag south of the area by the end of Monday, yielding generally dry and cooler conditions heading into the extended. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 210 pm Friday: Forecast confidence is relatively high for roughly the first 24 hours of the extended range. After that, everything goes to pot in the anticipated complex split flow regime. There are essentially two model camps for the latter half of next week: the GFS camp and the ECMWF/Canadian camp. The latter camp is more potent with a mid-week southern stream disturbance, while the GFS is more sheared/out and suppressed. As such, the GFS is almost completely dry for our area during the Tue night/Wed time frame, while the other model camp develops the next round of widespread precip during this time frame. There`s enough of a signal there to advertise solid chance pops, but would like to see more of a consensus before going any higher than that. If precip does develop early enough Wed, there may be, as usual enough cold air in place to support a brief/low impact winter weather event across the mountains Wed morning. By Day 7, the GFS is more progressive and much stronger with a southern stream upper low originating from the Four Corners region...also maintaining a distinct split flow pattern while the ECMWF/Canadian camp begins to phase the flow be the end of the forecast period. As such, the GFS has a blockbuster storm system impacting the forecast area by next Friday, while the other camp is essentially dry. Again, there`s enough in the guidance to support a small pop, but 20-30% is as far as we`re willing to reach at this point. Temps are forecast to return to more sane levels during the medium range, generally within a category or so of climo through the period. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: Sfc high that is set up shop off the New England coastline will continue to push in N to NE winds to all TAF sites with the exception of KAVL. Rain will continue into the overnight hours, but a warm front to the south will eventually lift over the area and shift winds to come out of the S and SW during the morning hours Saturday. The main axis of moisture will lift with the frontal boundary during the same time frame, but steady cloud cover will keep cigs at IFR levels with LIFR possible during the overnight period. Vsbys will likely continue to deteriorate as well through the overnight period with IFR/MVFR restrictions likely. Flight restrictions should ease a little bit after daybreak on Saturday, with MVFR conditions expected through lunchtime and possible VFR during the afternoon and evening. This will be short-lived as restrictions will likely return after sunset Saturday with cigs and vsbys expected to lower with rain chances returning on Sunday. Outlook: Sct to numerous showers and associated flight restrictions are expected to persist thru the weekend and into early next week, with drying expected on Tuesday. Confidence Table... 01-07Z 07-13Z 13-19Z 19-00Z KCLT High 82% Med 71% High 81% High 93% KGSP Med 76% Med 72% High 85% High 94% KAVL High 90% High 82% Med 76% High 91% KHKY High 89% High 82% High 81% High 87% KGMU Med 76% High 83% High 90% High 95% KAND Med 70% Med 69% High 86% High 89% 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...Winter Weather Advisory until 10 PM EST this evening for NCZ033. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...CAC SHORT TERM...JDL LONG TERM...JDL AVIATION...CAC is the U.S. government's official web portal to all federal, state and local government web resources and services.