Area Forecast Discussion
Issued by NWS Charleston, SC

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813 FXUS62 KCHS 261000 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 600 AM EDT Sun May 26 2024 .SYNOPSIS... Hot conditions are expected through Memorial Day. A cold front will move into the region Monday night and stall into mid week. High pressure will return for the second half of the week. && .NEAR TERM /THROUGH TONIGHT/...
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The forecast is on track. No changes were needed for the sunrise update. Today through This Evening: The region will remain aligned along the western flanks of a southwest-northeast oriented subtropical ridge that extends from the eastern Gulf of Mexico to just offshore of the Southeast U.S. coast today. A weak perturbation is forecast to cross the area this afternoon and evening as the local area remains pinned between Atlantic high pressure offshore and lee-side trough extending from the Upstate into western Virginia. Most of the morning hours looks to remain rain-free, but rain chances will begin to increase away from the coast late this afternoon into this evening as strong mixed layer instability featuring MLCAPE 2000-2500 J/kg develops within a ribbon of higher 850 hPa theta-e located across the interior. Vertical cross section suggest the approaching mid-level perturbation will not result in a tremendous amount of forcing, but enough will be present to support isolated showers/tstms. Most of this activity looks to develop across the Midlands and CSRA by mid-afternoon, which will then propagate into the far interior areas by late afternoon and continue into the early evening hours. Despite the development and inland push of a modest resultant sea breeze circulation, considerably lower 850 theta-e values and resulting unfavorable K-indices will likely preclude the development of deep convection across the coastal counties. The only except could be across parts of coastal Colleton and Charleston Counties where activity over the Midlands could make a run for the middle South Carolina coast this evening. Slight chance pops were highlighted across the interior and into the Charleston Metro Area this afternoon and evening. Modified soundings support DCAPE values of 1000-1400 J/kg with steep low-level lapse rates near 7.0 C/km so there will be risk for damaging winds with any tstms that develop with the greatest chances occurring roughly along/north of Walterboro to Johns Island line coincident with the corridor of highest 850 theta-e values. A low-end risk for marginally severe hail also exists with WBZ heights holding around 11.5 kft; however, hail stones will tend to melt fairly quickly as they fall through an increasing warm sub-cloud layer. It will be another seasonably hot and humid day with highs warming into the lower 90s with a few mid 90s possible in a few areas. These temperatures combined with moderate levels of humidity will support heat indices in the 98-101 range. Overnight: Dry conditions will prevail into early Monday morning once evening convection dissipates. A little ground fog could develop prior to daybreak, but no major issues/impacts are expected. It will be warm/humid night with lows only dropping into the lower 70s with mid 70s at the coast and beaches. The record high minimums could be challenged, mainly at the Charleston AFB/International Airport (KCHS) and Downtown Charleston (KCXM), but current data suggest values will fall just short of record levels.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY/... The forecast area will be situated between offshore high pressure and a cold front approaching from the west on Monday. Aloft, broad troughing shifts towards the East Coast, pushing the ridge axis offshore. Consensus keeps at least the first half of the day dry, then upstream convection could move into the area later in the afternoon and into the evening/overnight. Still unsure of how much coverage there will be when this occurs but at least scattered showers and thunderstorms will be possible. Some of this activity could be more organized when it arrives. Primary threat with any stronger storms would be damaging wind gusts. Otherwise, expect another hot day with highs reaching the low 90s in most locations. Lows Monday night will largely be around 70 or in the lower 70s. The aforementioned front will then stall in the vicinity into mid week. PWats fall and trends have continued to show a drier forecast for Tuesday. Shouldn`t see more than just isolated showers and thunderstorms, particularly along the coast. A dry forecast is in place for Wednesday. Highs both days peak in the upper 80s to lower 90s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... High pressure will be the primary surface feature Thursday into the weekend. Aloft, mid level wave passes over the Northeast and Mid- Atlantic, before shifting offshore late week. This period should be mostly dry, aside from some diurnal rain chances returning over the weekend. Temperatures will be near normal. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/...
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26/12z TAF Discussion: KCHS/KJZI/KSAV: VFR for much of the period. Satellite shows a small pocket of stratus centered just south of KRBW. These clouds may get close to KCHS at daybreak, but latest trends suggest a slight erosion along the cloud bank`s eastern flanks. There are no plans of including stratus at this time unless last minute trends suggest otherwise prior to issuance time. Isolated showers/tstms are expected this afternoon and evening with the best chances holding inland from the terminals. Some of these could make a run for KCHS by early evening, but confidence of activity that terminal is too low to justify a mention at this time. Extended Aviation Outlook: Brief flight restrictions are possible in showers/thunderstorms Monday afternoon into Tuesday.
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&& .MARINE... Today: West winds will turn more southerly this afternoon with the development of a modest resultant sea breeze circulation. Winds along the land/sea interface, including Charleston Harbor, could get a bit elevated for a few hours this afternoon with winds in the Harbor reaching 15 kt with gusts to 20 kt. Onshore winds coupled with an outgoing tide could make for locally rough conditions in the Harbor late this afternoon. Seas will average 1-2 ft. Tonight: Southerly winds around 10 kt will persist through the night. A few tstms could move off the Charleston County coast later this evening bringing a risk for convective wind gusts in excess of 34 kt and cloud-to-water lightning. Monday through Friday: Marine conditions remain below Small Craft Advisory levels through the week. South to southwest will largely persist through midweek until a cold front pushes east of the waters. High pressure will be the dominant feature for late week. Winds will average 15 knots or less and seas 2-3 feet, with occasional 4 feet early in the week. && .CLIMATE... Record High Minimum Temperatures: May 27: KCHS: 76/1991 KCXM: 79/2019 KSAV: 77/1878 May 28: KCHS: 76/2000 KCXM: 80/2000 KSAV: 76/1885 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$