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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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539 FXUS62 KCHS 291747 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 147 PM EDT Sat Jun 29 2024 .SYNOPSIS... Atlantic high pressure will prevail this weekend, while a trough of low pressure resides inland. A cold front is expected to impact the area Monday into Tuesday. High pressure will return for the latter half of next week. && .NEAR TERM /THROUGH TONIGHT/... This afternoon: No significant changes for the early afternoon update. Convection a bit slower to form than CAMs have been indicating. The temperatures were also a bit slower to rise, but in the last 30-60 minutes, most of them have popped into the lower 90s away from the immediate coast. The issue continues to be little in the way of large scale forcing for showers/thunderstorms. Scattered convection well inland has been slowly advancing eastward, with only very isolated showers trying to develop within the seabreeze, especially around Charleston. Expect convection to become more active within the next hour or two, with at least scattered showers and thunderstorms to be near the coast within the seabreeze and additional scattered convection inland. Higher coverage possible in the interior as the convection over the interior interacts with any convection within the slowly westward advancing seabreeze. Outflow boundaries from any convection will also play a role in developing additional convection. Highs still on track to be in the lower to mid 90s across areas away from the immediate coast. With surface Tds in the lower to mid 70s, it will feel very uncomfortable, but not reaching Heat Advisory criteria. Tonight: Similar to the previous night, mild and humid conditions will be in place for the night. A few showers and/or thunderstorm can not be ruled out with boundary interactions early evening, but activity will likely be waning with diurnal heat loss. Late night, a continued onshore wind could drive a few showers onshore. Patchy fog is also possible late, mainly for locations that see rain during the day. In general, low temps will range between the mid 70s inland to upper 70s/around 80 near the beaches. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... High pressure will be situated offshore on Sunday, while a trough of low pressure resides inland ahead of an approaching cold front. Main drivers of convection will be daytime heating and the sea breeze and then along the inland trough which could eventually move into the local area later in the day and into Sunday night. Ample instability near or over 2000 J/kg will be present but shear doesn`t look particularly impressive. Widespread organized severe weather is not expected, but a few strong to severe thunderstorms with gusty winds are possible, in addition to locally heavy rainfall with PWats well over 2 inches. Also of note is the heat. High temps largely in the mid 90s will combine with elevated dew points to make it feel even hotter. Heat indices are forecast to top out in the 105-109F range. Heat Advisories will be possible for some areas, but worth noting that convection could disrupt temperature trends and heat indices may not reach the 2 hour duration requirement. Lows only fall to the mid/upper 70s. The aforementioned front will sink into the area late Sunday night into Monday. It looks to be a fairly active day with numerous to widespread showers and thunderstorms expected. Activity generally looks to shift south and east through the day as drier air tries to work in behind the front. A couple strong to severe storms will be possible along and ahead of the front in the afternoon/evening with slightly better wind fields and sufficient instability. Damaging wind gusts would be the primary hazard. It will not be quite as hot, with highs ranging from the upper 80s near the Santee River to low 90s south near the Altamaha. The front will stall nearby into Tuesday before eventually dissipating. Additional showers and thunderstorms will be possible, with best coverage in the south in proximity to better moisture, but the trend overall has been drier. It will be notably cooler than previous days, with highs mainly in the mid to upper 80s. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Mid level ridge builds over the Southeast for mid to late week. Atlantic high pressure will largely prevail at the surface, with a trough of low pressure eventually developing inland. Large scale subsidence under the ridge will help limit convection, but isolated to scattered diurnally-driven showers and thunderstorms will still be possible. Main concern looks to be the return of the heat. Still several days out, but the set-up does appear to bring the potential for excessive heat headlines. && .AVIATION /18Z SATURDAY THROUGH WEDNESDAY/... KCHS/KJZI/KSAV: Have not made any significant changes to the previous forecast for the remainder of this afternoon and evening. In general, VFR conditions still expected to prevail through much of valid 18Z TAF cycle. However, tempo MVFR cigs/vsbys are possible at CHS/SAV terminals later this afternoon within any showers/thunderstorms along an inland moving sea breeze. Left VCSH for KJZI for next few hours today, but think convection will generally stay just inland of the site. Any convection is expected to dissipate after sunset with VFR conditions prevailing. Extended Aviation Outlook: Prevailing VFR. Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings. && .MARINE... This afternoon: No significant changes were made to the previous forecast, with no highlights expected. A weak pressure gradient will remain in place across the waters along the western periphery of high pressure extending across the Atlantic and south of a stationary front positioned across the Mid-Atlantic states. Winds/seas generally south-southwest around 10-15 kt or less with seas no higher than 2-3 ft. Peak winds should occur near the coast, when a sea breeze circulation develops and shifts inland early afternoon. Sunday through Thursday: Southerly flow will persist Sunday into Monday with speeds 15 knots or less. Winds turn to the northeast/east Monday night into Tuesday as a cold front sinks through the waters and high pressure ridges in from the north. The high will eventually shift offshore and remain the primary feature through late week. No marine headlines are expected. Seas average 2- 3 feet. Waterspouts: We`re well into the local "Waterspout Season", and an in-house Waterspout Index provides us with a Moderate Risk this morning with light winds, weak shear, and ample low-lvl moisture in place. Much will depend if a land breeze lingers and/or a line of cumulus develops along a boundary this morning. Rip Currents: Latest guidance indicates a Moderate Risk for rip currents along all beaches today. Given the weekend is here, have opted to maintain the Moderate Risk for today. A Low Risk is in place for all beaches Sunday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...DPB/RFM SHORT TERM...ETM LONG TERM...ETM AVIATION...DPB/ETM/RFM MARINE...DPB/ETM/RFM