Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 261127 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 627 AM EST Fri Feb 26 2021 .SYNOPSIS... A cold front will remain stalled south of the region today as high pressure builds over to the north. Gulf moisture will return over the front today through tonight. The boundary will retreat northward as a warm front through the weekend, 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 before unsettled weather likely returns to the region through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... 620 AM Update...latest temp trends are a little warmer than fcst/d, so updated the hr/lys as well as maxT, which will occur arnd daybreak. Still expect sfc ridge to build in a little stronger later this morning and bring cooling conds into the afternoon as td/s lower as evap cooling commences. PoPs look good as first precip shield is now bringing -shra across the wrn most zones. Cloud cover will increase this morning as the FA remains in a sw/ly channeled flow aloft while sfc hipres ridges in from the NE. Expect precip to begin across the NC mtns and NE GA arnd daybreak and become more widespread across the rest of the FA throughout the day as pockets of ulvl vort energy traverse the region. The increasing dyno lift will combine with mech lift over the srn NC mtns and produce decent rainfall rates with rainfall amts adding up to arnd 2.0 inches in localized areas by late this evening...and this could create some minor hydro issues in this area. The WPC still has the area in a marginal risk for excessive rainfall, which seems okay at least for the srn NC mtns and srn BR. Elsewhere, rainfall amts will generally remain under an inch thru tonight, with the srn most zones likely only receiving a half inch or less of rainfall. Temps will fall during the day as a cold cP airmass works in from the NE and high temps will be reached arnd daybreak, then drop into the u30s to l40s by the afternoon. The latest NAM is still more certain of an ice event across the far nrn NC mtns, mainly Avery county this afternoon, as noted by it/s quite cold partial thicknesses. The GFS on the other hand has a cold partial thickness trof in the same area as well, yet sigfnt/ly warmer. Thus, have blended the thermal profiles of these two models and ran a top down approach for wintry precip. This gave a couple tenths of ice accum across the higher elevs of Avery arnd Beech Mtn, which makes sense given the amt of precip expected in that area between 18z-00z. So, the winter weather advisory will be continued for more of a -fzra concern with this package. Temps tonight will also be non/diurnal as the wedge breaks down and a strong warm nose aloft lowers to the sfc. Temps shud start rising after midnight, but only a couple degrees leading to readings arnd 40 F most areas by daybreak Sat. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 230 am EST Friday: Deep-layer southwesterly flow will set up over the region by Saturday between a trough digging through the Rockies to the west and a shallow ridge axis over the Atlantic to the east. The lingering surface wedge boundary should retreat northward through the day on Saturday, with modest rain shower chances the best over the NC mountains and north of I-40. The southwesterly upper flow will persist through weekend, and the deeper moisture and forcing will continue to wrap mainly west and north of the forecast area through much of the weekend ahead of an approaching cold front. Lingering low-level moisture and occasional upglide will likely lead to more cloudiness than not through the weekend, but with thicknesses steadily climbing and maxes reaching the upper 60s in the mountain valleys to lower or even middle 70s east of the mountains Sunday afternoon. Much deeper moisture along the frontal boundary sagging southeast will arrive on Sunday night. Heavy rainfall could occur at times, especially in the southern NC mountains, where a few nighttime rumbles of thunder will be possible as well. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 230 am EST Friday: Progressive northern tier energy will brush the region Monday through Monday night, while a closed southern stream system remains much slower to move east from the Four Corners region to north Texas. Ahead of the northern stream forcing, a cold front and associated moisture will cross the region early Monday and settle southeast of the area Monday night. Mainly morning PoPs will pare away from the northwest by late Monday, but with uncertain clearing of the southern tier Monday night depending on the boundary`s progress. 1030+ mb surface high pressure will then build from the Midwest to the mid-Atlantic coast Monday night through Tuesday, spilling chilly thicknesses down across the region and producing temperatures a couple of categories below climo in most areas by Tuesday afternoon. The southern stream system should open up and then reach the southern Appalachians by Tuesday night, with a return of briefly deeper moisture. The main question centers around how quickly upglide moisture returns ahead of this wave, with PoPs increasing through Tuesday, but with maximum PoP values more likely Tuesday night. Brief ptype issues will be possible in the NC mountains depending on the precipitation timing. Model solutions then become out of phase Wednesday through Thursday, with the ECMWF featuring a central CONUS trough while the GFS indicates a shallow ridge axis moving east. However, sensible weather differences are actually not that stark despite these differences given a westerly component to the low-level flow and somewhat limited moisture. So, will feature mainly low end chance PoPs for now on Wednesday and Thursday with temperatures rebounding to near, or slightly above, climatology. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: VFR flight conds currently will begin to deteriorate aft sunrise across most TAF sites as hipres ridging in from the NE will interact with a moist frontal boundary thru the period. Expect MVFR conds to persist at KCLT a little longer than the other TAF sites, but then drop into IFR/LIFR late evening and persist thru the period. Across the other terminals, IFR conds will likely develop arnd the earlier afternoon and be maintained thru the evening. Periods of heavier rain and lower VSBY associated with passing upper energy will cross the FA from the west and have short-lived TEMPO groups to account for this possibility generally beginning and ending arnd mid to late morning. Winds outside the mtn valleys will become defined more ne/ly with low-end gusts today as the sfc high builds in. Outlook: Widespread precip and associated flight restrictions developing today are expected to persist into the weekend and possibly extending into early next week. Confidence Table... 11-17Z 17-23Z 23-05Z 05-06Z KCLT High 80% Med 75% High 80% High 100% KGSP High 100% High 90% High 90% High 94% KAVL High 100% Med 70% High 100% High 89% KHKY High 100% Med 75% High 85% High 100% KGMU High 100% High 80% High 90% High 94% KAND High 100% High 80% High 80% 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: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Winter Weather Advisory until 10 PM EST this evening for NCZ033. SC...None. && $$ SYNOPSIS...HG NEAR TERM...SBK SHORT TERM...HG LONG TERM...HG AVIATION...SBK

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