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Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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691 FXUS62 KGSP 311357 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 957 AM EDT Fri May 31 2024 .SYNOPSIS... Dry high pressure centered over the region will keep temperatures slightly below normal with dry weather persisting through Saturday. High pressure shifts offshore Sunday with warming temperatures and increasing moisture. A more active stretch of weather may return early next week with daily afternoon thunderstorm chances within a summer like pattern. Another cold front will approach the area late week. && .NEAR TERM /THROUGH TONIGHT/... As of 9:45 AM Friday...A thin layer of cirrus continues to spread over our area from the west. Winds have already picked up at several sites with a handful of sites reporting low-end gusts. Still expect the winds to weaken as we move into the afternoon and the larger- scale pressure gradient diminishes as the sfc high slides further south. Otherwise, an upper level trof axis shifts east today as a strong ridge builds in from the west and the area comes under the influence of stg subsidence. This will keep the column mostly dry the period as PWAT values drop about 0.9 inches below normal. Strong convec to the west will bring in a good amt of upper clouds, but low-lvl clouds will be limited to the mtn ridges as LCLs become quite dry east. Surface high pressure becomes reinforced to the north during the aftn and srn ridging will advect dry air more efficiently across the ern zones. Thickness values don`t change much today and with reduced insol, expect highs held few degrees below normal. Surface td/s will vertically mix better across the ern zones due to a more energized mixed layer, which will lower afternoon RH values to less than 25 percent east of I-26. Relative humidity will likely hold in the mid 30 percent range west. No sigfnt fire-wx issues are anticipated as winds generally remain less than 10 kts with a limited low-end gust potential. Decent rad cooling tonight and calming winds will allow min temps to drop 6-8 degrees below normal across the area. A late morning dense fog threat is negligible, however, as sfc td/s only increase to the mid 40s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 204 AM Friday: The short term forecast period starts off Saturday morning with a tall shortwave ridge extending along the spine of the Appalachian Mountains. Farther west, a compact shortwave trough is progged to be located over the Lower Mississippi Valley. At the surface, sprawling high pressure will still be entrenched across much of the East Coast with an associated very dry continental airmass. Forecast PWATs Saturday morning around or below 0.5" would be well below the 10th percentile for early June and near daily record low values based on Greensboro sounding climatology. As such, a dry forecast will prevail on Saturday with temperatures remaining a couple ticks below average. By Saturday night into Sunday, surface high pressure will quickly slide offshore with weak southerly return flow returning across the southeast states. At the same time, the previously mentioned shortwave trough over the Lower Mississippi Valley will lift northeast across the Ohio Valley and into the central Appalachians. Associated rain chances will return across the mountains which will be in closer proximity to a deeper plume of moisture. Uncertainty exist farther east as to how quickly moisture will return with return flow trajectories still emanating out of a local ThetaE minimum in the wake of the departing surface high. Will carry at least a slight chance of showers and storms across the Piedmont with the greatest rain chances confined to the mountains. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 216 AM Friday: A more typical summer pattern appears poised to return early to middle next week. Persistent onshore flow will support continued moisture recovery with dewpoints rising back into the mid 60s amidst 1.5-2" PWATs. Aloft, a weak westerly flow regime will be draped from the Southern Plains to the Southern Appalachians. The 00z suite of global guidance depicts several embedded shortwave perturbations that will slowly make their way into the area early next week. Exactly how these waves evolves remains uncertain with GFS and CMC solutions attempting to close off an upper low while the ECMWF and ICON camp paints several more progressive/weaker waves. Regardless, the combination of passing waves and a very moist atmosphere should prove sufficient to instigate mainly diurnally driven showers and thunderstorms Monday through Wednesday, especially across the mountains. Forecast soundings are not overly supportive of a severe weather threat with very moist profiles, near moist adiabatic lapse rates, and very tall/skinny CAPE profiles. A couple locally strong water loaded wet microbursts cannot be ruled out and will need to be assessed on a daily basis. By late week, guidance depicts an intense Pacific jet diving into British Columbia and the Pacific Northwest. This in turn carves out a deep and negatively tilted trough across the Central and Northern Plains by Wednesday morning. This trough then swings across the Great Lakes and into the Ohio Valley. An associated cold front will race across the Great Plains and towards the region by Thursday. Guidance begins to diverge at this point with regards to timing of the front and location/amplitude of the large scale trough. A more organized severe weather threat could accompany the front, but will be dependent on eventual evolution of the upper trough and strength of the front. Another surge of dry continental air with near daily record low PWATs will bring a return of dry weather Friday into next weekend. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... At KCLT and elsewhere: VFR trends continue thru the 06Z TAF cycle. Some mlvl StCu will persist this morning thru daybreak arnd KCLT and the Upstate terminals, but cloud cover returns to mainly Ci outside of afternoon FEW/SCT Cu across the NC mtns. Winds remain calm/light thru daybreak then align ne/ly to ene/ly after inversion break outside the mtns with speeds generally 6-8 kts. Afternoon winds at KAVL align se/ly. Winds go variable to calm once again across the FA tonight. Outlook: VFR and dry weather through Saturday. Convective chances return late this weekend and will linger into next week. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...TW NEAR TERM...JPT/SBK SHORT TERM...TW LONG TERM...TW AVIATION...JPT/SBK