Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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851 FXUS62 KGSP 071730 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 130 PM EDT Fri Jun 7 2024 .SYNOPSIS... High pressure will slowly filter in across the area today, following the departing cold front, leading to drier conditions through Saturday. Shower and thunderstorm chances return on Sunday as another cold front tracks across the Carolinas. Forecast confidence lowers starting next week as the overall pattern is uncertain by the end of the seven day period. && .NEAR TERM /THROUGH TONIGHT/... As of 1130 AM EDT Friday: Isolated to scattered cu have developed across portions of the forecast area this morning while cloud cover continues to thin near/along I-77. No major changes were needed as the forecast remains on track. The axis of an upper trough will gradually develop east of the forecast area today, with lower theta-E filtering into the CWA in the wake of a departed frontal boundary. Surface dewpoints are expected to dip into the 50s...if not the 40s this afternoon, resulting in anomalously low RH, mostly sunny skies, and virtually no instability. Chances for diurnal convection are therefore essentially 0. Max temps are expected to be slightly above climo. The relatively dry air will result in rather large diurnal temp ranges, with min temps tonight expected to be around 5 degrees below normal under continued mostly clear conditions. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 200 AM EDT Friday: Dry conditions will linger through Saturday as weak high pressure sets up shop over the southeastern CONUS. The flow aloft remains out of the west-northwest as an upper-level low centered over eastern Canada and New England will send a trailing cold front across the Midwest and gradually encroach the CFWA through the forecast period. Embedded vort energy will present within the west-northwest flow aloft, while the area of high pressure slowly slips offshore during the daytime period Saturday. As a result, a return flow in the low-levels will increase dewpoints with lee troughing developing east of the mountains. Some of the global models suggest the potential for an MCS to form within the mean flow and send it towards the region late Saturday into early Sunday, ahead of the main frontal boundary, but uncertainty in run to run trends lower confidence, especially considering the airmass will remain rather stable and dry. In this case, have a hard time seeing any type MCS reaching this far east, but could disrupt the overall temperature forecast due to the potential cloud debris that may reach the area as heating begins on Sunday. Otherwise, the front will continue to inch closer to the CFWA by Sunday. PWAT values rise back above 1.50" as the front enters the area and the global models suggest that up to 1500 J/kg of sbCAPE could be available ahead of the front, with the exception of the Canadian. Not much in the way of forcing as the better dynamics remain well to the north and only very subtle height falls suggest that the trailing front will have a hard time initiating much in coverage, especially east of the mountains. However, this is the Summertime and a front will be present with high PWATS, so still going to stick with mentionable PoPs for Sunday afternoon/evening as the front pushes into the CFWA from the northwest, but coverage is in question at this point until we get a better read from the CAMs. The overall consensus is for the front to make a complete fropa, but some of the 00Z guidance actually stalls the boundary just south of the CFWA and sets up a potential unsettled pattern for Monday. Temperatures are expected to run near-normal Saturday, while rising as high as ~5 degrees above-normal Sunday as the area settles under the warm sector of the encroaching frontal boundary during peak heating. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 AM EDT Friday: Overall synoptic pattern starts to differ amongst model guidance by the start of the extended forecast period. The GFS stalls the aforementioned frontal boundary and cuts off a closed low that drifts from the Northern Great Plains into the OH Valley, while the stalled boundary activates and a stout low pressure system develops over the southeastern CONUS. This would provide multiple days of heavy rainfall and could lead to a hydro threat, if this scenario played out. However, the ECMWF stalls the frontal boundary as far south as the Gulf Coast and allows for a continental surface high to filter in from the northwest and low-amplitude upper ridging slowly building across the Eastern Seaboard by the middle part of the week, with the Canadian favoring the ECMWF. In this case, the sensible weather would remain dry and rather pleasant for June, but forecast confidence remains low as global models diverge significantly through D7. The GFS brings in drier air behind the low pressure system as it pushes northeast and dry high pressure filters in behind by D6/D7. The ECMWF shifts the continental high offshore and brings in a return flow, which will lead to diurnal showers and thunderstorms during the same time frame. The Canadian continues to follow suit with the ECMWF through much of the medium range. Decided to run with the NBM mostly, but did adjust PoPs down slightly due to the uncertainties. Temperatures are forecasted to run at or slightly above normal through the upcoming workweek. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... At KCLT and elsewhere: VFR and dry thanks to high pressure building into the western Carolinas from the west through the 18Z TAF forecast period. FEW to SCT VFR cumulus have develop across the terminals this afternoon. Cumulus should dissipate shortly after sunset. Low-end gusts will continue at KAVL through early this evening before tapering off. KAND just started seeing low-end gusts this afternoon but these are expected dwindle later this afternoon. Clear skies are expected overnight with a FEW cirrus expected to track over the terminals on Saturday. Winds east of the mtns will remain NW through late this evening before toggling more N (with some sites even seeing winds go NNE) overnight. Winds will remain NW at KAVL through the 18Z TAF period. Winds east of the mtns will gradually turn WSW/SW by early Saturday afternoon. Wind speeds will generally be lighter on Saturday compared to today. Outlook: A cold front brings shower and thunderstorm chances back on Sunday. Activity may linger into early next week due to the front stalling along the Southeast Coast. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...CAC NEAR TERM...AR/JDL SHORT TERM...CAC LONG TERM...CAC AVIATION...AR