Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 221523 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1123 AM EDT Sun Jul 22 2018 .SYNOPSIS... A broad upper low will drop south across the Ohio Valley today, then settle across the Deep South Monday through Wednesday. This low will remain nearly stationary and support moist unsettled weather across the region. The low will weaken late in the week, as another cold front approaches from the northwest. && .NEAR TERM /THROUGH TONIGHT/... As of 1110 AM: The forecast appears on track this morning with only minor adjustments to a slightly delayed start on scattered convection along the ridge tops. Otherwise, the western Carolinas and northeast GA will be positioned to the west of the deep moisture associated with broad warm conveyor belt region, and to the east of the mid-level deformation zone, this afternoon through tonight. However, this should allow most of our area to receive decent insolation this afternoon, albeit with temperatures remaining a couple of degrees below climo under the anomalously low heights. Despite significantly weaker mid-level lapse rates, the atmosphere is expected to become moderately unstable this afternoon. Thus, the favorable location to the east of the upper trough axis, the approach of the next mid-level speed max rotating around the cyclone, along with W/NW low level upslope flow across the TN Valley/southern Appalachians should allow the high terrain to light up with numerous convective coverage by mid- afternoon. Mean W/SW winds in the cloud-bearing layer will tend to sweep high terrain convection into the NC foothills and western Piedmont by late afternoon, so while likely pops are carried north of I-85 in NC, pops taper to only 30% across much of the northeast GA and Upstate Piedmont. Establishment of weaker mid/upper level flow in the vicinity of the trough axis, along with generally unidirectional profiles will shunt the substantive shear east of our area today, which combined with anticipated modest levels of instability will limit the severe convective potential to perhaps a couple of pulse events, certainly much less of a threat than on Saturday. Locally heavy rainfall may be of slightly higher concern, but even then, PWATS will be quite subdued through the near term, basically right around climo. Convection will diminish in coverage through the evening, but gradually developing low level southeast flow may allow for showers to linger near the escarpment into Monday morning. Min temps are expected to be a bit below climo. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... As of 300 AM EDT Sunday: An upper low will continue to slowly drift south and weaken Monday, settling roughly over central GA by Tuesday. This will keep the forecast area within a favorable region for weak, though persistent deep-layer Q-vector convergence. The low- level flow will gradually back from southwesterly to southeasterly by late Monday, bringing in Atlantic moisture into the region. The 00z models seem to be shifting a bit east with the plume of very moist PWATs, keeping it along the Mid-Atlantic coast. We should still have periods of numerous showers with some embedded tstms, capable of producing torrential downpours. Isolated flooding concerns will likely exist starting Monday evening thru at least Tuesday night, perhaps more focused across the eastern half of the CWFA. Temps will feature a below average diurnal range under plenty of clouds. Highs a couple categories below normal and lows at or slightly above normal. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 330 EDT AM Sunday: The weak upper low over the Southeast will finally open up and shear out, as a northern stream trough digs into the Great Lakes on Wednesday. That trough may close into another upper low and stall out, keeping a trough axis just west of the CWFA thru the end of the work week. An associated cold front will push in from the NW and stall out along a SW-NE axis across the Southeast. This will likely keep above climo PoPs thru at least Friday. The latest GFS and ECMWF keep unsettled weather across the CWFA right thru next weekend. Overall, temps are expected to return to near climo and convection should be more diurnally driven than during the middle of this week. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... ...AMD NOT SKED CARRIED AT KAND DUE TO ASOS OUTAGE... At KCLT and Elsewhere: Scattered to numerous coverage of showers and thunderstorms is anticipated again this afternoon/evening, with the best chances existing across the NC mtns/foothills, warranting categorical mention of SHRA/VCTS at KAVL and KHKY this afternoon, TEMPO at KCLT, and Prob30s elsewhere. The potential exists for multiple rounds of showers and storms at all terminals later today, so the convective mention is carried for 6+ hours at most sites. Lingering low level moisture will pose another threat of fog and/or patchy low cigs early Monday, but restrictions will be most likely in areas that receive rainfall this afternoon/evening. Since we don`t know that for sure attm, will generally pass the buck for adding late night/early Monday restrictions. Outlook: An active/wet period is expected to continue through the middle part of next week as a slow-moving storm system impacts much of the East. Numerous showers and thunderstorms are expected during this period. While there will likely be an afternoon/evening peak in coverage on most days, higher-than-normal chances will also exist during the overnight and morning hours. Confidence Table... 15-21Z 21-03Z 03-09Z 09-12Z KCLT High 100% High 100% High 100% High 97% KGSP High 100% High 100% High 100% High 100% KAVL High 98% High 100% High 94% High 84% KHKY High 100% High 100% High 100% Med 72% KGMU High 100% High 100% High 100% High 98% KAND High 100% High 100% High 100% High 92% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: www.weather.gov/gsp/aviation && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...ARK NEAR TERM...HG/JDL SHORT TERM...ARK LONG TERM...ARK AVIATION...HG/JDL

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