Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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030 FXUS62 KCHS 192205 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 605 PM EDT Thu Sep 19 2024 .SYNOPSIS... An area of high pressure is expected to gradually strengthen across the region through early next week. A weak cold front may approach from the west by next Thursday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Ongoing shower activity will dissipate pretty quickly after sunset, possibly lingering a tad longer over parts of the Charleston Tri-County into Colleton County. The boundary layer will once again decouple quickly after sunset resulting in calm to light/variable winds. The best fog parameters look to setup across parts of Southeast Georgia again tonight, although 1000 hPa condensation pressure deficits look marginal. The mention of "patchy fog" was expected a bit into interior Southeast South Carolina with a mention of "areas of fog" over parts of interior Southeast Georgia where the axis of best fog parameters look to align. Lows from the upper 60s inland to the lower 70s at the beaches and Downtown Charleston. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Friday: The axis of the mid-level trough is expected to push east over the western Atlantic as strong ridge centered over TX ridges NE over the Ohio River Valley. GFS indicates that a short wave is expected to track from north to south across the forecast area during the afternoon, followed by rising heights. As temperatures reach the mid to upper 80s over dewpoints in the 70s, weak instability should develop across extreme SE GA. Latest run of the HREF indicates that a weak sea breeze may develop along the GA coast Friday afternoon. The combination of the shortwave passage, weak sea breeze, and limited instability may support isolated showers along the coast of SE GA during the afternoon. Saturday and Sunday, the forecast area will become dominated by weak sfc high pressure as a large H5 ridge builds across the Deep South and Southeast U.S. GFS forecast soundings indicate that the environment will remain less than 1.6 inches of PW with a significant inversion at H8. High temperatures should favor values in the upper 80s, with low 90s possible across inland GA on Sunday. PoPs will remain less than SCHC through this weekend. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Monday through Tuesday: Long term guidance indicates that the H5 590 DM ridge will shift east across the northern Gulf coast and FL. This ridge combined with a low over the western Caribbean could set up a Rex Block through early next week. H5 heights should increase across the forecast area, peaking Monday and Monday night, limiting any instability across the forecast area on Monday and Tuesday. The forecast will feature dry weather through early next week. High temperatures are forecast to remain in the mid to upper 80s. Wednesday: H5 heights will begin to break down, possibly with the approach of amplifying wave. GFS shows a cold front accelerating east, possibly pushing across the forecast area by Wednesday evening. The forecast will feature SCHC to CHC PoPs for showers and thunderstorms. High temperatures will generally range in the mid 80s. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... 20/00z TAF Discussion: KCHS/KJZI/KSAV: Another round of fog/stratus will impact the area tonight. The bulk of this should remain west of the terminals with VFR conditions prevailing. The risk for MVFR vsbys in fog is highest at KSAV and KJZI. The fog will mix out quickly after sunrise. Extended Aviation Outlook: No significant weather expected. && .MARINE... Tonight: Easterly winds late the afternoon and evening will become northerly late tonight. Winds generally remain 10 knots or less with seas averaging 1 to 3 feet. Friday through Monday: Building high pressure should result in winds between 10-15 kts with gusts around 20 kts. Wave heights should generally remain between 2-5 ft. Conditions should remain below Small Craft Advisory criteria. && .TIDES/COASTAL FLOODING... Given high astronomical tides and latest tidal departures, minor coastal flooding is expected along the Charleston and Colleton county coasts with the evening high tide cycle. A Coastal Flood Advisory has been issued with tide levels expected to peak between 7.3-7.5 ft MLLW. Further south and along the Georgia coast, current forecast keeps tides from reaching minor flooding criteria of 9.5 ft MLLW in Fort Pulaski, but will continue to monitor trends. Positive tidal anomalies along with high astronomical tides from the full moon will lead to elevated tides for the rest of this week and through the weekend. Coastal Flood Advisories will probably be needed for both the morning and evening high tides through Friday for both Charleston Harbor and Fort Pulaski. The astronomical high tides start to lower Saturday and Sunday, but the morning high tides will likely be elevated enough to still require Coastal Flood Advisories (especially for Charleston and coastal Colleton Counties). More uncertainty exists for Fort Pulaski. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Coastal Flood Advisory until midnight EDT tonight for SCZ049- 050. MARINE...None. && $$