Area Forecast Discussion
Issued by NWS Greer, SC

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000 FXUS62 KGSP 170752 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 352 AM EDT Tue Sep 17 2019 .SYNOPSIS... A cold front will drop southward through the area today and tonight, with cool, surface high pressure building in behind this feature, and remaining in place through the end of the week. && .NEAR TERM /THROUGH TONIGHT/... As of 345 AM EDT Tuesday: Aside from patchy mountain valley fog, expect conditions to remain dry and quiet across the area this morning, with temperatures in the low to upper 60s. As Hurricane Humberto continues to churn well off (and slowly away from) the Carolina coast this morning, a weak backdoor cold front just to the north will drop down through the area today, as upper ridging continues to shift eastward overhead. As a result, expect increasing clouds today, with the potential for isolated showers and thunderstorms. Into tonight behind the front, as showers/tstorms gradually taper off, cool sfc high pressure will begin to build in from the NE - the beginning stages of the wedge scenario on tap for rest of the week. Temperatures today will be above normal once again, but the warmest day of the rest of the work week. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM EDT Tuesday: The short term begins Wednesday morning with upper ridging stretching from the TX Gulf Coast to the Great Lakes, Humberto off the East Coast moving toward Bermuda and slowly phasing with a deep trough off eastern Canada, and another trough pushing into the Pacific Northwest. Surface high pressure in place over eastern Canada under the confluent flow aloft will dam down the eastern slopes of the Appalachians, with a marked change in temperatures in store...10 to in some areas almost 15 degrees cooler for highs on Wednesday than what we`ll see today. Orographic lift combined with a little wave moving down the northerly flow aloft will lead to some precip chances especially across the mountains, though certainly not a wash-out. Much cooler temperatures for Wednesday night as well. The upper ridge will elongate to the northeast as we move into Thursday, but the damming will remain even as the parent high slides south toward Long Island. Another really beautiful day in store for Thursday with skies clearing and highs again 3-5 degrees below seasonal normals. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 310 AM EDT Tuesday: Damming high will be in place as we move into the extended, but with the upper ridge continuing to shift east, the high will slide toward the Carolinas and continue to moderate as it does so. Northeasterly winds will shift around to southeasterly as the high works toward the region. As we move into the weekend, the western trough will push east along the northern tier, forcing the upper ridge to stretch E-W across the South and Gulf Coast, and the surface high will push just offshore. Expect a slow warming trend through the period, such that by early next week we`ll be back 5-7 degrees above normal. At the end of the period, a weakening cold front will be approaching the area and may bring some showers to the mountains, but otherwise no rain expected through the period. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... At KCLT and elsewhere: Despite anticipated mountain valley fog this morning, do anticipate VFR will prevail at all TAF sites through the morning hours, though could not entirely rule out brief MVFR at KAVL towards daybreak. However, given lower confidence, have not introduced it attm. This afternoon, expect increasing coverage of VFR cloud cover with isolated to scattered showers and thunderstorms as a weak back door cold front drops southward through the area. SHRA/TSRA activity could linger into the overnight hours, but given lower confidence, have not highlighted this in going fcst. Winds overall will NE AOB 5 kts. Patchy areas of fog towards the end of the valid TAF period is possible. Outlook: Anticipate the return of VFR by Wednesday afternoon. Dry high pressure builds in for the end of the week, with just some mountain valley fog each morning for restrictions. Confidence Table... 08-14Z 14-20Z 20-02Z 02-06Z KCLT High 100% High 100% High 100% High 95% KGSP High 100% High 100% High 100% High 98% KAVL High 100% High 100% High 100% High 89% KHKY High 100% High 100% High 100% Med 63% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 89% 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...SGL NEAR TERM...SGL SHORT TERM...TDP LONG TERM...TDP AVIATION...SGL

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