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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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906 FXUS62 KCHS 141124 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 724 AM EDT Wed Aug 14 2024 .SYNOPSIS... A cold front will move slowly south of the area early morning. High pressure will then build from the north into late week. Another cold front may approach the area early next week, then remain nearby through late week. && .NEAR TERM /THROUGH TONIGHT/... Early morning update: No significant changes made to the going forecast. Following an area of low stratus migrating down through southeast Georgia that will bring a few hours of cloudy conditions to that area. Low clouds will erode/lift through the morning hours. Previous discussion... Overnight analysis reveals upper level troughing from New England down into the Carolinas, downstream from ridging that stretches from the Upper Midwest to the Texas Gulf coast. Large expanse of surface high pressure is across the Great Lakes/Ohio Valley region, expanding into the southeast CONUS. Surface boundary extends off the southeast Georgia coast near Altamaha, northeastward into the Atlantic with a fair amount of post- frontal stratus expanding out of southeast SC into southeast GA within the shallow cooler air mass that`s spreading into the region. Quiet weather persists for the most part, although there is a thin line of convection off the SE SC coast, perhaps along an old outflow boundary that migrated into the coastal waters. Surface high pressure will continue to expand into New England and the Mid Atlantic through tonight with some semblance of a wedge pattern setting up through the Carolinas into Georgia. This will drive a relatively cooler and drier air mass into the region and bring a needed break from the hot/humid conditions of late. Precip-wise: Despite the lowering boundary layer moisture/dewpoints, with suppressed upper level heights and slightly cooler temperatures aloft, daytime heating will generate a few to several hundred J/Kg MLCAPE this afternoon across southeast SC and bit higher values through southeast GA. There may be enough low level convergence along the coastal marine layer/sea breeze this afternoon to kick off some convection...primarily along the southeast GA coastal corridor where higher dewpoints/instability will reside. But overall precip coverage will be diminished today as compared to the last few days. Highs today will run from the mid to upper 80s across South Carolina to the upper 80s to lower 90s in Georgia. Tonight: Any showers/storms that do develop will fizzle this evening with quiet weather through the night. Cooler nighttime temperatures with lows in the upper 60s to lower 70s inland, to the middle 70s along the coast. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... Thursday and Friday: Aloft, a broad trough will shift offshore, becoming more distant across the Atlantic while deep layer ridging extends across the Deep South and Southeast. This will help drive drier air across the region, with PWATs decreasing to around 1.5 inches and a light northeast wind maintaining mostly rain-free conditions across the entire area Thursday, and likely through Friday despite a more direct onshore wind returning locally. Temps will also be slightly cooler despite mid-lvl ridging and full days of sun, while overnight temps will become noticeably cooler as stronger radiational cooling takes place under clear/mostly clear skies and light/calm winds. In general, highs should range in the mid-upper 80s, warming a degree or two higher on Friday. Lows should dip into the mid-upper 60s inland and low-mid 70s closer to the coast. Saturday: Aloft, the mid-upper ridge will start to shift offshore as a deep low tracks across the Great Lakes region and toward the Northeast during the weekend. Troughing will take place south of the feature, with h5 vort energy rounding its southern edge toward the Southeast. This should bring a few showers and/or thunderstorms well inland as a light southerly wind advects deeper moisture back to the region, but mainly late day as upstream convection drifts into western most zones before nightfall. Afternoon highs should be slightly warmer than the previous day, generally peaking in the upper 80s near the coast to low-mid 90s inland, warmest across Southeast Georgia. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... A cold front extending south from a parent low passing across the Northeast/Mid-Atlantic states is anticipated to approach the Southeast United States early next week, potentially stalling nearby into mid-week before another mid-lvl trough forces it further offshore heading into the second half of the week. The pattern should favor more unsettled weather conditions Sunday through Wednesday while the front and h5 shortwave energy provide sufficient forcing across ample moisture. Temps should be within a few degrees of normal for this time of year with highs generally in the upper 80s to lower 90s and lows in the low-mid 70s. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... Area of IFR stratus continues to migrate down through southeast Georgia and will bring a period of IFR conditions to KSAV early this morning. Stratus will erode/lift through the morning with conditions returning to VFR by 16Z. Some afternoon showers and thunderstorms are possible, although coverage will be less than in recent days and probabilities of impacting a particular terminal are low. 12Z forecasts will continue to show VCSH after 18Z-19Z timeframe until early evening to account for this. Any showers/storms that develop will fade this evening with VFR conditions prevailing through early Thursday morning. Extended Aviation Outlook: VFR conditions will likely prevail at CHS/JZI/SAV terminals through Saturday. Brief flight restrictions come early next week to all terminals as a front brings showers/thunderstorms to the region Sunday. && .MARINE... Northeasterly winds will dominate across the coastal waters through tonight with a touch of gustiness (around 20 knots) developing later this morning and through the afternoon/early evening. Seas 3 feet or less this morning will build to 3 to 4 feet through the day, possibly touching 5 feet in the outer Georgia waters. Wednesday: No highlights expected as a backdoor cold front pushes south of the waters through this period. Expect east- northeast winds of 10-15 knots with some gusts to near 20 knots possible. Seas generally 3 to 4 feet. Thursday through Sunday: High pressure will build across the Southeast United States Thursday into Friday while Tropical Cyclone Ernesto tracks northward far offshore across the Atlantic. Conditions are expected to remain below Small Craft Advisory levels into Friday morning, with east-northeast winds averaging around 10- 15 kt along with a few gusts up to 20 kt on Thursday becoming more easterly on Friday. However, seas are expected to build through late week due to increasing swells associated with Ernesto, which could lead to Small Craft Advisories across offshore Georgia waters Friday and Saturday for 6-7 ft seas, and potentially across nearshore waters Friday night into early Saturday with 6 ft seas making it as close as 10 nm from the shore. 6 ft seas could linger across offshore Georgia waters into Sunday, but conditions should improve sufficiently to where Small Craft Advisories are less likely with south-southwest winds between 10-15 kt and seas generally between 3- 5 ft. Rip Currents: Risk for rip currents will likely increase late this week, as swells from distant Tropical Cyclone Ernesto impact the beaches. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...TBA SHORT TERM...DPB LONG TERM...DPB AVIATION...TBA/DPB MARINE...TBA/DPB