Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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531 FXUS62 KCHS 221930 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 330 PM EDT Wed May 22 2024 .SYNOPSIS... High pressure will persist into late week. Diurnal convection and hot temperatures expected during the holiday weekend. A cold front might bring impacts to our area on Tuesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Although there were isolated showers early in parts of southeast Georgia earlier, they have since dissipated, and we have removed mention from the forecast. Maybe a stray shower forms along the sea breeze across interior Georgia prior to sunset, but that`s it. Diurnally induced cumulus will fade with sunset, leaving us with mainly clear skies through the night. However, late at night there are indications of some stratus and potentially some fog developing. We maintained mention of patchy fog after 4 am, but most guidance implies that it won`t be as bad as it was in some places during this morning. That`s likely due to us having a difficult time achieving our cross-over temperatures. Radiational cooling will again prevail as winds become light or calm in most places with the sunset, offset somewhat by the synoptic flow that turns southerly. Lows will be down in the lower and middle 60s far inland, upper 60s and lower 70s closer to the coast, in downtown Charleston and downtown Savannah. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday: The day will begin with the H5 ridge along the coast, shifting east through the afternoon. A shallow H5 trough will slide over the southern Appalachians during the afternoon. At the sfc, a wavy front should remain across the Ohio River Valley, with moisture pooling to the east. Short term guidance indicates that a weak sea breeze may develop Thursday afternoon. However, with poor lapse rates lingering llvl CIN should keep the forecast area dry. High temperatures are forecast to range around 90 degrees. Friday, the H5 heights will remain generally zonal with a weak trough across the Coastal Plain in the afternoon. Isolated to scattered showers and thunderstorms are forecast to develop along a sea breeze Friday afternoon. Given sfc conditions in the low 90s and dewpoints in the upper 60s to low 70s, a wide field of instability should develop during the heat of the afternoon. Saturday, models indicate that broad H5 trough will develop across the Southeast U.S. At the sfc, a weak trough is expected to form along the coast, reinforced with an afternoon sea breeze. High temperatures will once again favor values in the low 90s. However, dewpoints should increase, generally ranging in the upper 60s to around 70. Deep moisture convergence and instability along and west of the sea breeze should support isolated to scattered thunderstorms. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Mid-level ridging should build across the region on Sunday. The forecast area will remain between deep low pressure over the Ohio River Valley and high pressure over the eastern Gulf of Mexico. This pattern should provide the region with deep south winds. Given the ridge overhead, showers and thunderstorms should hold off until the afternoon and evening, forming along the sea breeze. Sunday is expected to be the hottest day, with mid 90s possible across the forecast area. The H5 ridge will remain across the forecast area on Monday. Sfc high pressure over FL is expected to ridge northward across the CWA. The forecast will continue to feature isolated to scattered showers and thunderstorms with highs in the low 90s. A cold front is forecast to impact the region on Tuesday. At this time, the forecast will feature PoPs in the high chance range. With the late arrival of the front and convection, temperatures may reach the low 90s. Wednesday, temperatures may range a bit cooler, with values in the upper 80s. Slight dryer conditions should result in lesser coverage of afternoon and evening showers and thunderstorms. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... VFR through at least most of the time through 18Z Thursday. Patchy fog is possible between 09Z and 13Z Thursday morning, possibly leading to a brief period of sub-VFR conditions. Extended Aviation Outlook: Mainly VFR through Thursday night. Brief flight restrictions are possible due to showers/thunderstorms each afternoon/evening beginning on Friday. && .MARINE... This evening and tonight: High pressure extends atop the local waters, leading to a fairly relaxed gradient. Once sea breeze circulations fade this evening, winds that start out SE`erly willveer around to the S or SW. Speeds on average won`t be anything more than 10 or 12 kt, and seas are 3 feet or less. At this time it does not appear that a repeat of the fog/stratus from this morning will happen again as we get close to daybreak Thursday. Extended Marine: High pressure should yield typical summer-time weather across the forecast area. In fact, a sea breeze is expected to develop each afternoon through the holiday weekend. A cold front may arrive on Tuesday, bringing an increase in thunderstorm activity. Otherwise, conditions should remain below Small Craft Advisory conditions. Rip Currents: On Thursday, the combination of astronomical influences from the Full Moon and a small swell will lead to an enhanced risk of rip currents at all of our beaches. The in-house Rip Current Calculator continues to indicate a Moderate Risk, while the Rip Current MOS points to a Low Risk. For consistency, we maintained the Moderate Risk. Rip currents are most likely at Tybee Island. && .TIDES/COASTAL FLOODING... Tidal departures have come down near 0.8 ft MLLW in Charleston Harbor. These departures might rise a bit due to southeast winds around 10-12 mph with the sea breeze. But comparing the past several high tides with the departures at the preceding low tide (they were almost the same), this would suggest that we don`t reach levels where minor coastal flooding begins. So no Coastal Flood Advisory is planned. Minor flooding is briefly possible with the evening high tides through Thursday along coastal Charleston and coastal Colleton Counties. There are no concerns along the remainder of our coast. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...