Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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255 FXUS62 KGSP 122351 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 751 PM EDT Sun May 12 2024 .SYNOPSIS... As low pressures approach from the west, moisture increases to start the week and rain returns to our area Monday afternoon and evening. Rain and thunder are expected on Tuesday and Wednesday, followed by a brief period of dry conditions on Thursday. Another low pressure arrives for next weekend bringing more rain. && .NEAR TERM /THROUGH MONDAY/... As of 745 PM: The forecast continues to be on track as we head into the evening. Expect gradually thickening high clouds, light wind, and slow temp drop thru the evening. Otherwise...ridge axis now situated over the lower MS Valley with attendant sfc high extending over the Cumberland Plateau. These features will build east tonight, and sfc winds will come around to the NE across the Piedmont. Sfc/upper low in the Plains will activate a warm front to our southwest overnight, but it looks pretty unlikely any of that precip will develop into our area in the morning. PoP onset has been delayed compared to previous fcsts, with dry air to overcome and the lift being relatively weak. Midlevel clouds however will increase in numbers overnight, but slow enough that decent radiational cooling still should occur, so still went with bias-corrected guidance blend similar to what has worked well in recent nights. Of particular note, the pattern still may permit eventual development of in-situ CAD but see no need to expect that will begin tonight, without precip. Warm front will shift northward over the sfc high in the morning, possibly resulting in light precip developing near the Blue Ridge Escarpment and in NE GA by noon. Abundant alto/cirrus cloud cover will be in place but low clouds are appreciably slower to develop. Guidance mostly holds off with QPF until after 18z, with saturation occurring from the top down. Still favor precip chances no better than chance range for the majority of the CWA, the exception in the Escarpment/GA areas where saturation appears to occur earliest; those areas will see likely PoP mention by late afternoon. Thus, formation of CAD probably will not be until after peak heating, but the cloud cover will impact highs especially SW of I-26 where they should be in place more or less all day. Lack of CAD also suggested by model consensus for winds going southerly across the CWA by late morning. We end up with highs several degrees below climo in the SW, but near or slightly above normal in the sunnier NE. Any convection afforded by the upglide likely will be too shallow to result in thunder. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 100 PM EDT Sunday: We remain on track for the likihood of dreary sensible wx conds Monday night as a period of moist llvl upglide flow expands atop of wedge-like pattern. Widespread low overcast, rain, drizzle and fog is on tap. Energy rounding the base of potent Ohio Valley upper low will eject NE into the region on Tuesday. Along with an associated slug of deeper moisture, showers are expected to be widespread. It remains probable that the wedge front, present along the SE fringes of the cwfa to start off the day, will be able to erode, probably uncovering a small amount of positive SBCAPE values SE of I-85 Tuesday afternoon. Within the robust deep shear there remains the possibility of svr tstm development along and SE of retreating/dissipating wedge front into Tuesday evening. The cwfa is progged to be within a cleaner warm sector environment on Wednesday, all beneath cyclonically curved flow aloft thanks to the lingering, but departing upper low axis. As temperatures warm to seasonable mid-May levels, the atmosphere will becoming moderately unstable. Coverage of diurnally enhanced tstms should becoming numerous, especially in Western NC where the flow and forcing will be greater. There should exist enough shear to promote a few severe storms. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 200 PM EDT Sunday: Save for the small chance for isolated ridgetop forced showers, we are expecting an essentially suppressed atmosphere on Thursday as upper ridge axis translates atop the SE CONUS. Lower elevations will warm into the lower 80s. The next slug of southern stream deeper moisture and energy remains progged to quickly advect into the cwfa on Friday. The latest medium range guidance is in decent enough agree with respect to the mass fields on Friday with considerable convective response, so the inherited sensible wx featuring numerous diurnally enhanced thunderstorms will remain as is. Less than usual confidence exists regarding the specifics for next weekend but with the wavy pattern likely to linger along with spokes of southern stream energy rippling eastward, above climo pops will be featured each day. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Cirrus will continue to steadily thicken and lower from SW to NE, with bases lowering to 15 to 18 kft by daybreak Monday. High pressure pushes east of the Appalachians allowing mainly NE winds tonight, which should all turn S/SE in the morning. Guidance is in good agreement on continued gradual moistening from the top-down thru the day Monday, with MVFR cigs possible across the Upstate sites after 18z, spreading to KCLT late evening or just after midnight Monday night. Scattered -SHRA will spread in from the SW along with the lower cigs, so will add PROB30 for potential impacts. Not expecting any TS with this activity thru the 00z TAF period. Outlook: Widespread precip and restrictions developing Mon night, with scattered thunderstorms developing Tue and Wed afternoons bringing a chance for periodic restrictions. Some nocturnal restrictions remain possible Tue and Wed nights. Brief drying expected Thursday. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...ARK/Wimberley SHORT TERM...CSH LONG TERM...CSH AVIATION...ARK