Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 222359 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 759 PM EDT Wed May 22 2019 .SYNOPSIS... High pressure will dominate and will produce unseasonably hot conditions through the middle of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Now that the sea breeze has passed inland of our counties, there is no longer any mention of convection in the forecast. The weak back door cold front is found near the Beaufort-Jasper border and drifting south-southwest. It is expected to move into Georgia as it crosses the Savannah River during the mid evening hours. Perhaps a few showers will occur due to this feature, but odds are too low to include in the forecast. The SREF is showing 30-40% chances of late night fog and stratus across our inland Georgia zones, but since those places will have the hardest time reaching their cross-over temps, we died not add to the forecast. Previous discussion... As of 4 PM: Latest satellite indicated small-celled Cu across SE GA and along the coast. Towering Cu with a few showers were pushing inland across the Charleston Tri-county. Based on the latest CAMs, the convection is timed to push west of the forecast area by 22Z. I will highlight the passage of the showers and isolate thunderstorms with SCHC PoPs. This evening, convective clouds will gradually dissipate across the CWA. A weak pressure gradient should result in light to calm winds tonight. The light winds combined with partly cloudy sky should yield low temperatures in the low to mid 70s tonight. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday: A weak backdoor cold front combined with the sea breeze to support a few showers over northern counties Wednesday. The weakening remnants of this cold front will shift into southern counties Thursday and could combine with the sea breeze to produce a few brief showers/thunderstorms Thursday afternoon. Thus, introduced PoPs around 15 percent to account for this scenario across southern counties. However, coverage of showers, if any, will remain sparse, and most areas will remain rain-free. Otherwise, high temperatures will average in the upper 80s to lower 90s at most locations. Well inland, a few locales could top out in the middle 90s, while highs in the lower/middle 80s should remain common on the beaches. Low temperatures Thursday night will range from the middle/upper 60s inland to the lower/middle 70s on the beaches. Friday and Saturday: Building high pressure at the surface and aloft will push our region into a significant heat wave that challenge or break many temperature records and will persist through Memorial Day weekend and at least into the middle of next week. Friday, expect high temperatures in the middle to upper 90s and maximum heat index values around 100F away from the beaches. Saturday, inland high temperatures in the upper 90s/lower 100s will be accompanied by maximum heat index values 101-106F. Despite these unseasonably hot conditions, strong subsidence/capping provided by the upper ridge will likely prevent any shower/thunderstorm development Friday and Saturday. During the overnight hours, a few inland locations could briefly dip into the upper 60s before daybreak, but most locations will only bottom out in the lower to middle 70s, some 5-10 degrees below normal for late May. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... High confidence in the first several days of this period as the very significant and hazardous early summer heat wave continues. The strong upper level ridge will shift a bit southwest of the area. This will aid in deep northwesterly downslope flow across the area with the sea breeze likely being pinned at or near the coast at least Sunday and Monday. With no significant change in 850 mb temperatures from the end of the short term period, high temperatures on Sunday, Monday, and quite possibly Tuesday will be hot, mainly near 100 away from the coast. Heat indices will likely reach Advisory levels Sunday through Tuesday in portions of the area. By Wednesday forecast becomes more uncertain with the GFS indicating a slight break in the heat wave while the ECMWF indicates that the heat wave is maintained or even worsens. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Mainly VFR. A period of lingering MVFR ceilings at KCHS early in the 00Z TAF period. At most a passing -SHRA might occur at KSAV tonight with a cold front moving in, but with no impacts. Extended Aviation Outlook: VFR. && .MARINE... Gusty winds will end as the sun sets this evening. The rest of the night should feature steady E-SE winds as high as 15 kt south and in Charleston Harbor, with 15-20 kt north, before dropping around 5 or 10 kt by midnight. Seas will average 2-3 ft within 20 NM and 3-4 ft beyond 20 NM. Thursday through Monday: High pressure and an associated pressure pattern will hold winds/seas well below Small Craft Advisory levels through this period. E/SE winds Thursday will give way to S/SW winds for the balance of this forecast period. Much of the time, winds should remain below 15 knots. However, given the intensity of the inland heat, the sea breeze could become fairly strong especially Friday through Memorial Day, perhaps locally pushing into the 15-20 knots range for a few hours each day. Seas should remain capped at 2- 3 feet through the period. && .CLIMATE... A very significant, hazardous and prolonged heat wave will challenge or break many of these records. RECORD FOR WED 05/22... Station Record High Min Year ------- --------------- ---- KCXM 76 1998 RECORD FOR THU 05/23... Station Record High Min Year ------- --------------- ---- KCXM 77 1998 RECORDS FOR FRI 05/24... Station Record High Year(s) ------- ----------- ------- KCHS 97 1953 KSAV 98 2011, 1953 KCXM 98 1953 RECORDS FOR SAT 05/25... Station Record High Year(s) ------- ----------- ------- KCHS 97 2000, 1953 KCXM 95 1962, 1953 KSAV 100 1953 Station Record High Min Year(s) ------- --------------- ------- KCHS 75 1953 KCXM 79 1998 KSAV 76 1878 RECORDS FOR SUN 05/26... Station Record High Year(s) ------- ----------- ------- KCHS 98 1953 KSAV 100 1953 KCXM 99 1953 Station Record High Min Year(s) ------- --------------- ------- KCHS 75 1998 KCXM 79 1998 RECORDS FOR MON 05/27... Station Record High Year(s) ------- ----------- ------- KCHS 98 1989 KCXM 95 1962, 1926 KSAV 98 1989, 1962 Station Record High Min Year(s) ------- --------------- ------- KCHS 76 1991 KCXM 78 1991 KSAV 77 1878 RECORDS FOR TUE 05/28... Station Record High Year(s) ------- ----------- ------- KCHS 97 1967, 1964 KCXM 93 2000 KSAV 96 1964, 1898 Station Record High Min Year(s) ------- --------------- ------- KCHS 76 2000 KCXM 80 2000 KSAV 76 1885 RECORDS FOR WED 05/29... Station Record High Year(s) ------- ----------- ------- KCHS 95 1945 KSAV 98 1945, 1898 KCXM 97 1921 Station Record High Min Year(s) ------- --------------- ------- KCHS 74 1991 KCXM 77 1998 KSAV 75 1885 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...SPR LONG TERM... AVIATION... MARINE... CLIMATE...

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