Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 231049 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 649 AM EDT Thu Mar 23 2017 .SYNOPSIS... Cooler air lingers across the region through the end of the work week. A warm and moist southerly flow develops this weekend as high pressure moves off the coast and a cold front approaches from the west. This will bring showers and thunderstorms into the area by Sunday, which continue into early next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 645 AM EDT...Stubborn stratocu continues to develop over the Upper Savannah Valley and western Upstate, affecting temps and warranting an adjustment to the sky grids. But otherwise, the forecast is on track. As of 300 AM EDT...An upper ridge will build over the region today, as a trough closes off into an upper low over the Colorado Rockies. At the surface, high pressure will settle over the Mid-Atlantic today, bringing the winds around from NE to SE. Forecast soundings show a shallow layer of RH trapped under a strong subsidence inversion around 5-7 kft. Southerly flow in that layer will keep enough moisture and WAA to produce a stratocu deck, mainly across the western third of the CWFA today. Otherwise, skies should be mostly sunny. thicknesses support max temps about 5-8 degrees below normal. Tonight, as low-level high pressure drifts off the coast, southerly flow will increase atop the CWFA, tapping into a little Atlantic moisture. Both the NAM and GFS show some increase in stratus across the Upper Savannah Valley, and possibly spreading up the Piedmont overnight. So I will advertise an increase in clouds across the western two-thirds of the CWFA by daybreak Friday. The depth of moisture doesn`t look deep enough in the time-heights to support precip. So will continue a dry forecast overnight. Min temps will be at to slightly above normal.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... As of 215 AM EDT Thursday: An upper ridge axis moves into the area Friday then slides to the coast Friday night. The center of surface high pressure wedged into the area from the NE in cold air damming pattern moves out into the Atlantic with the ridge taking on an east-west orientation. This allows a moist southerly flow to begin to develop creating isolated showers near the Blue Ridge along the NC/SC/GA border. Highs Friday will be near to a little above normal. Lows Friday night will be 5 to 10 degrees above normal. An upper low moves into the mid MS valley Saturday and into the OH valley Saturday night as a short wave rotates around the upper low and into the TN valley. The surface ridge breaks down as a cold front associated with the upper low moves toward the area. This creates a stronger moist southerly low level flow. Deep moisture moves in as well along with synoptic scale forcing. Precip chances will slowly increase Saturday with best chance along the southern Blue Ridge, but then quickly increases Saturday night with best chances over the mountains and foothills. Highs will be 5 to 10 degrees above normal with lows 10 to 15 above normal. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 345 AM EDT Thursday: Guidance remains in good agreement during the medium range. The upper low moving east in the short range moves into the Mid-Atlantic on Sunday swinging the associated short wave across our area. Deep moisture and synoptic scale forcing move through as well as a cold front approaches from the west. Precip chances increase as a result then slide east Sunday night with the short wave. There will certainly be enough instability and forcing for thunderstorms to develop. Shear increases as well. This combined with the forcing may be enough to produce isolated severe storms. Precip chances continue Monday and Tuesday as another, albeit weaker, upper low and associated short wave crosses the area. Again, there will be enough instability for thunderstorms to develop. However, with the weaker upper system, shear is much less with a much lower severe storm chance. Ridging builds in surface and aloft on Wednesday bringing an end to precip chances. Temps 5 to 10 degrees above normal Sunday rise to 10 to 15 degrees above normal through the end of the period. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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At KCLT and Elsewhere: VFR conditions expected through the period, except for some MVFR cigs around the Upstate and NE GA early this morning. The low clouds are expected to scatter out within an hour or two of the 12z TAF issuance. However, a thin layer of moisture trapped under an inversion around 6 to 7 kft will persist thru the day and tonight over much of GA and into the western Upstate. The associated cloud deck may expand north and east overnight tonight. Some guidance, in particular the NAM, hints at MVFR stratus developing again across portions of central GA and Midlands and expanding toward the Upstate and KCLT sites right before daybreak Friday. I will only mention that at KAND for now. Winds will favor NE thru midday, then veer to SE this afternoon. Winds will back somewhat again tonight, especially across the Upstate to ENE, but should remain SE at KCLT thru the rest of the period. A few low-end gusts will be possible at KAND, but otherwise, winds should stay 10 kts or less thru the period. Outlook: Low level moisture begins to return from the south tonight thru Friday, resulting in an increase in cigs. Some restrictions in stratus may be possible Friday and Saturday mornings, especially near the Blue Ridge escarpment. Precip chances return Saturday thru Sunday. Confidence Table... 10-16Z 16-22Z 22-04Z 04-06Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 100% High 100% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% 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
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&& .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Freeze Warning until 9 AM EDT this morning for NCZ035>037-056- 057-069-072-502-504-506. SC...None. && $$ SYNOPSIS...RWH NEAR TERM...ARK SHORT TERM...RWH LONG TERM...RWH AVIATION...ARK

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