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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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615 FXUS62 KCHS 161820 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 220 PM EDT Tue Jul 16 2024 .SYNOPSIS... High pressure will persist offshore, while a weak trough resides inland through mid week. A cold front will approach the region late week and likely stall nearby. && .NEAR TERM /THROUGH TONIGHT/... 17Z SPC mesoanalysis 1-2K J/Kg MLCAPE across the forecast area with minimal CINH. Afternoon satellite image shows building Cu primarily along and west of the I-95 corridor and showers west more inland toward the Midlands. Another batch of showers/storms is ongoing farther south toward the JAX ea. But thus far, shower/storm development is lacking across our forecast area. Still monitoring trends. Despite the instability, low level convergence across the forecast area does appear to be a bit more limited as compared to the last few days. It`s noteworthy that recent high-res guidance has and remains rather minimal with convection this afternoon, particularly the HRRR. That said, it wouldn`t take much to trigger convection. Will see how convection/outflows progress upstream and locally along the marine layer over the next few hours. Tonight: Convection will gradually wind down with rain-free conditions prevailing after midnight. It will remain warm and humid with lows from the mid 70s well inland to the lower 80s at the beaches and Downtown Charleston. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... Ridging aloft will begin to break down on Wednesday as a broad trough amplifies into the southeastern states. At the surface a cold front will begin to approach the region, likely stalling in the vicinity of the Carolinas late in the week. PWATs ahead of the cold front will increase to over 2 inches along with moderate to strong instability. With some synoptic forcing from the approaching front combined with the local sea breeze, scattered to numerous showers and thunderstorms are forecast to develop each afternoon, with PoPs generally increasing as the week progresses. While the threat for organized severe thunderstorms is low, with DCAPE values forecast around 800 J/kg a strong to marginally severe thunderstorm cannot be ruled out. Conditions Wednesday and Thursday are expected to be hot and humid, with slightly cooler high temperatures on Friday as the cold front approaches. Heat Index values on Wednesday and Thursday are forecast to reach 105-107, with some locations reaching 108F. Heat Advisories may be required for portions of the forecast area. However, afternoon convection may hinder temperatures from reaching their full potential. Friday high temperatures are forecast to reach into the low to mid 90s, with Heat Index values of 102-105, below Heat Advisory criteria. Overnight low temperatures will provide little relief, only dipping into the mid 70s inland and upper 70s to around 80 along the coast. The record high minimum temperatures could be challenged at all three of the climate sites, see the Climate section for more details. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... Broad troughing aloft will prevail this weekend, with high pressure extending into the forecast area from the Atlantic early next week. At the surface, a front is forecast to linger in the vicinity of the Carolinas through the weekend, yielding elevated PWATs. Between lingering forcing from the nearby front and the afternoon sea breeze circulation scattered to numerous showers are forecast each afternoon. Guidance continues to be rather bullish with PoPs through the long term period, so the current forecast maintains chance to likely PoPs, still above climatology. With above normal precipitation chances and increased cloud cover through the period temperatures are forecast to return to near normal, or even slightly below normal through the weekend. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... 16/18z TAF Discussion: KCHS/KJZI/KSAV: VFR for much of the period through 17/18z. There remains is a risk for afternoon showers/storms this afternoon although nothing has developed near the local terminals thus far. KSAV may still have the best shot for direct impacts from convection late in the afternoon with lower chances at KCHS/KJZI. Forecast has maintained VCTS and TEMPO for TS at KSAV afternoon 22Z. But confidence is on the lower side. Extended Aviation Outlook: Scattered afternoon showers/tstorms could produce brief flight restrictions at all terminals this week. && .MARINE... Today: Modest nocturnal surging should end prior to daybreak. South to southwest winds will prevail today with sea breeze enhancements likely near the land/sea interface and Charleston Harbor as the sea breeze moves inland. Speeds will average 10-15 kt, but may be closer to 15 kt with gusts to 20 kt at the beaches and Charleston Harbor. Seas will average 2-4 ft. Tonight: Another modest noctural surge is expected, especially for the South Carolina waters north of the Savannah River Entrance. Winds will range from 15-20 kt in the South Santee- Edisto nearshore leg to 10-15 kt with gusts to 20 kt over both Georgia marine zones. Winds will remains somewhat tempered in the Charleston Harbor, but should still hold in the 10-15 kt range. Seas will average 2-4 ft. Wednesday through Saturday: High pressure will prevail across the marine zones while a cold front approaches the inland zones. This will yield a slightly pinched pressure gradient between the approaching cold front and the high pressure over the marine waters. Overall, conditions are expected to remain below Small Craft Advisory criteria. However, there is a chance that the Charleston nearshore waters could see wind gusts to 25 knots on Wednesday. Otherwise, generally S winds are forecast, 10-15 knots. Slightly stronger wind speeds are possible along the direct coastline in association with the afternoon sea breeze. Seas should average 3 to 4 ft. && .CLIMATE... Record High Minimum Temperatures: July 16: KCHS: 78/2023 KCXM: 82/2021 KSAV: 82/1883 July 17: KCHS: 78/2023 KCXM: 82/2021 KSAV: 80/1883 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory until 7 PM EDT this evening for GAZ116>119- 138>141. SC...Heat Advisory until 7 PM EDT this evening for SCZ043>045- 047>052. MARINE...None. && $$