Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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918 FXUS62 KCHS 210115 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 915 PM EDT Fri Sep 20 2024 .SYNOPSIS... High pressure will strengthen across the region through early next week. A weak cold front may approach from the west around the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Late evening GOES-E mid-level water vapor imagery shows shortwave energy dropping south along the Georgia and far southern South Carolina coast with an associated vorticity maximum positioned about 60 NM east/southeast of the Savannah River Entrance. This feature will moves steadily south tonight with DNVA/subsidence builds in in its wake. Earlier shower activity has dissipate with the loss of insolation and the diurnally driven cumulus field has dissipated. Clear to mostly clear skies will prevail. The boundary layer has decoupled inland with calm to light winds prevailing. Winds are holding up just a bit along the coast. Wind should pick up a bit just before daybreak as high pressure nudges south. While some patchy fog could develop across far interior Southeast Georgia and up along parts of interior Southeast South Carolina adjacent to the CSRA and Midlands, no major impacts are expected. Lows from the upper 60s inland to the lower 70s at the beaches and Downtown Charleston look good. Very few changes were needed for the late evening update. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... The mid-levels will consist of a trough just off the East Coast Saturday morning and ridging over the central U.S., with embedded high pressure over TX. By Monday, the trough will have shifted further offshore, pushed by the ridge that will have moved over the East Coast. Additionally, the embedded High should be over the FL Panhandle. At the surface, High pressure will remain over the Southeast U.S. Subsidence associated with the High is expected to bring mainly dry weather during the short term. We will note that most of the synoptic models are completely dry on Saturday. Though, the long-range CAMs are split between it being completely dry and some members showing light showers along the GA coast. PWATs are around 1.5", but many model soundings show decent dry air in place. So we opted to go with 10% POPs in these locations Saturday afternoon. If anything does manage to form, it will be isolated, brief, light, and may just be sprinkles. Saturday evening through Monday are completely dry. Temperatures will trend higher due to approaching ridge. Highs will be in the mid to upper 80s Saturday, and the upper 80s to around 90 degrees on Sunday and Monday. Though, it will be cooler at the beaches. Lows Saturday will be in the mid to upper 60s for most locations. Sunday night they`ll be in the upper 60s inland to the lower 70s along the immediate coast. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Surface high pressure will initially be over our region, then shift offshore mid to late next week. A cold front should approach from the northwest on Friday. This synoptic pattern will yield dry conditions through Wednesday, with increased POPs Thursday and Friday. High temperatures should be at or slightly above normal Tuesday and Wednesday, trending lower Thursday and Friday. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... 21/00z TAF Discussion: KCHS/KJZI/KSAV: VFR through 22/00z. Extended Aviation Outlook: There are no concerns. && .MARINE... Tonight: High pressure will increase across the marine zones tonight. Winds across the nearshore and outer waters will remain from the ENE around 10 kts this evening, increasing to 10-15 kts late tonight. Seas should range between 2 to 4 ft. Saturday: The interaction between High pressure inland and a weak trough south of FL will yield sustained NE winds 10-15 kt during the day. Winds will ease during the evening and overnight. Seas will average 2-4 ft during the day with some 5 footers in the GA waters from 20-60 nm. Seas should drop about 1 foot during the evening and overnight. Sunday through midweek: High pressure will prevail inland, then begin to move offshore midweek. Expect sustained winds to be mainly 10 kt or less. Seas will average 2-3 ft within 20 nm and 3-4 ft for the GA waters from 20-60 nm. && .TIDES/COASTAL FLOODING... A Coastal Flood Advisory continues through midnight for Charleston and Coastal Colleton for minor coastal flooding. Coastal flooding is likely again up and down the entire coast with high tide late Saturday morning. For Charleston Harbor, the current 7.9 ft MLLW forecast look solid. There is some concern that levels could get uncomfortably close to major flood levels (8.0 ft MLLW), but this scenario only has about 10% probability of occurrence. A Coastal Flood Watch for Charleston and Colleton Counties will not be issued with this forecast update for this reason. Fort Pulaski looks to say solidly in the minor flood category. Coastal Flood Advisories will be needed for all coastal zones from late morning into the early afternoon hours. Positive tidal anomalies and high astronomical tides from the recent full moon will lead to elevated tides through the weekend. Although the astronomical high tides are lowering, coastal flooding is expected with each daytime high tide cycle along the Charleston and Colleton county coasts. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Coastal Flood Advisory until midnight EDT tonight for SCZ049- 050. MARINE...None. && $$