Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 262356 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 756 PM EDT Mon Oct 26 2020 .SYNOPSIS... Warm and sunny conditions should return Tuesday under weak high pressure. Tropical Cyclone Zeta will reach the central Gulf Coast late Wednesday. Rainfall may be heavy at times Wednesday night and Thursday as Zeta`s remnants pass near the southern Appalachians. Conditions improve for Friday with cool, clear weather expected through Saturday. && .NEAR TERM /THROUGH TUESDAY/...
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As of 750 PM EDT: Much of the Piedmont has cleared out as we head into the evening, but plenty of lingering stratocu across mountains, foothills and the Upper Savannah Valley. The sky grids were updated to reflect these trends. Otherwise, the forecast is on track. Surface high pressure pushing off the New England coast will allow the wedge in place to gradually lose its grip on the area through Tuesday. The forecast will remain dry with the possible exception of a few showers associated with a weakening front near the Tennessee border through this evening. A short-wave ridge moving overhead tonight into Tuesday will sustain the lack of mid to high clouds. This combined with the retreating wedge is nearly the perfect recipe for low clouds and fog developing across much of the area tonight. Dense fog will be possible, especially near the mountains and across the I-77 corridor including the Charlotte area. Temperatures will bottom out into the 50s. The lack of mid to high clouds Tuesday should allow low clouds and fog to burn off fairly quickly with any dense fog dissipating by mid morning. The effects of the wedge should just be just a memory by Tuesday afternoon as the building ridge and weak downslope flow support a return to well above normal highs into the 70s.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 130 PM Mon: Weak sfc high pressure will remain over the area through Wednesday, with moist southwesterly flow aloft driven by an offshore upper ridge and the deep cutoff low over the Plains. An effective warm front will work its way north from the Gulf Coast Tuesday night, preceding TC Zeta. Subtropical moisture will spread over the CWA. Although this will warrant PoPs starting to ramp up, the better warm-frontal QPF is depicted to our west with that feature, so any precip that early looks relatively low-impact. A lull could even occur some of Wednesday. The models overall have narrowed their spread in terms of tracking Zeta near the southern Appalachians, but some solutions take the circulation west of the Escarpment and others east, and this leads to a relatively large spread in the ensemble QPF via the opposing effects of the terrain among those tracks. Additionally, the storm is generally shown to spend more time over the Gulf and near the coast, which suggests it will reach our area a bit later than originally thought, though certainly no slower in terms of forward speed. Strengthening low-level flow and upper divergence warrant a rapid increase in PoPs/QPF early Thursday; the pass of Zeta across (or nearest) our area now looks to occur morning to early afternoon Thursday. PWATs should easily exceed 2 SD above normal, perhaps closer to 3 SD. QPF numbers hug the WPC values, which reflect a track in the middle of the NHC cone, just south of the TN/NC border. This gives a quick hit of terrain-enhanced precip; while the rates will be impressive, it won`t be that long-lived of an event. Storm-total values are above 4 inches along the ridges near the Balsams and southern Escarpment, with 1 to 3 for the surrounding mountains and foothills. Still looking like the flood threat will be primarily in the more flashy spots in these areas, but certainly can`t rule out some minor issues elsewhere in the NW half of the CWA. SBCAPE progs have trended down overall, seemingly reflecting the consensus for Zeta to take a more easterly track, and possibly the later expected arrival. A warm sector still generally will exist ahead of the "other" low, which should track across the lower Ohio Valley Thursday. Thus, a small amount of instability potentially will remain over our area, post-Zeta. As shear parameters strengthen ahead of the front, our risk for isolated damaging wind events may continue to increase until it passes Thursday night or early Friday; on a positive note, however, veered near-sfc winds in the wake of Zeta would tend to limit the tornado threat. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 215 PM Mon: Precip should end for the most part early Friday behind the front; some lingering northwest-flow precip is possible later in the day, but that should taper off with additional drying. Furthermore, precip likely will end before temps cool enough to support any change to snow. Gusty winds will taper off Friday evening; dry and rather settled conditions will continue through Saturday under sfc high pressure. That high may prove transient, being associated with a relatively flat upper ridge that some models depict moving offshore Sunday ahead of a fast-moving trough. A small PoP could end up returning to the forecast by Sunday, but confidence is too low for that on this cycle. Max temps will be several degrees below normal over the weekend, with mins near normal. With light winds, a few areas likely will see frost. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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At KCLT and elsewhere: Guidance is mixed on the development of fog and low stratus across the area tonight. It looks a little more favorable for fog (which could become dense) across the NC Piedmont and the mountain valleys. But the Upstate, it looks more like a stratus event. Either way, there will likely be a period of MVFR to LIFR cigs, with areas of IFR or lower vsby). Lower confidence in the timing for return to VFR which is pegged between 14Z and 16Z for now. Light winds through the period. Outlook: Flight restrictions return Wednesday as the remnants of Zeta bring widespread rain low cigs/vsbys to the area. The most significant impacts will probably be Thursday. Conds will likely improve to VFR Friday. Confidence Table... 00-06Z 06-12Z 12-18Z 18-00Z KCLT High 95% Med 77% Med 79% High 89% KGSP High 85% Med 76% Med 79% High 98% KAVL Med 78% Med 73% High 88% High 97% KHKY High 88% Med 72% High 84% High 94% KGMU High 87% Med 77% High 82% High 99% KAND High 89% Med 62% High 81% High 97% 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:
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...Wimberley NEAR TERM...ARK/Munroe SHORT TERM...Wimberley LONG TERM...Wimberley AVIATION...ARK is the U.S. government's official web portal to all federal, state and local government web resources and services.