Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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499 FXUS62 KCHS 121053 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 653 AM EDT Wed Jun 12 2024 .SYNOPSIS... A stationary front will meander near or just off the coast through the end of the week. High pressure will build in from the north through the weekend, then shift east early next week. && .NEAR TERM /THROUGH TONIGHT/... The forecast area will remain under slight mid-level ridging through today. At the sfc, SE GA/SC should remain on the edge of weak high pressure centered over KY. A wavy front positioned from the northern Gulf of Mexico, across middle FL, and NE over the western Atlantic will remain nearly stationary today. This pattern should support steady ENE winds across the forecast area this morning. By this afternoon, temperatures are expected to range from the low 90s across the inland counties to the upper to mid 80s along the coast. A sea breeze should develop early this afternoon, pushing inland through the mid to late afternoon. Forecast soundings show a strong inversion centered at H7, with dry air aloft. The forecast area should remain dry today. It is interesting to note that some of the near term guidance indicates that a compact and deepening frontal wave will develop off the FL/GA coast over the Gulf Stream this afternoon. These guidance members then track the system to the NE along the front, spreading a plume of deep moisture west over the SC coast late tonight. However, nearly all guidance indicates that a broadening inverted trough will remain along the front. Given that a longwave H5 trough over the Deep South will slide east tonight, a solution indicating a weak spot low seems reasonable. Taking this compromise approach, the forecast will feature SCHC PopS approaching the SC coast late tonight. Low temperatures are forecast to range from the upper 60s inland to the low 70s along the coast. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... Thursday and Friday: An area of broad surface high pressure to our northeast will slide offshore Thursday as an upper trough, largely limited to the Mid-Atlantic, pushes a cold front toward the area from the northwest Friday night. A weak trough will develop along a stationary front positioned just off our coast Thursday, becoming slightly more defined by Friday. This will result in a fairly decent moisture gradient across the area with a relatively dry air mass well inland and a plume of deep moisture streaming northeast across the Florida Peninsula and into the Atlantic. Showers and thunderstorms will largely be limited to the coastal waters in proximity to the boundary and weak trough/low, but there could be enough moisture and instability to generate, at the most, isolated convection along the coast both days. The general thinking is that areas far inland will remain mostly rain-free, with coastal southeast Georgia being the prime location for potential convection initiation (where the greatest moisture is located). Any convection that does develop should diminish in the evening. Highs in the upper 80s to low 90s Thursday will increase to the mid 90s Friday. Lows will range from the upper 60s far inland to the lower 70s near the coast, and mid 70s along the beaches Thursday night. Friday night will warm slightly into the low to mid 70s. Saturday: As the weakening cold front pushes across the area Saturday, the coastal low will push further out into the Atlantic. Weak flow aloft will become replaced by a building ridge from the southwest. As a result, Saturday features rain-free conditions with mostly clear skies as subsidence over the area strengthens. A steady increase in temperatures will continue owing to the upper ridge. We could see highs reach the upper 90s most places, with the beaches staying a bit "cooler" in the low 90s. Although approaching dangerous levels, heat indices will stay shy of Heat Advisory criteria; ranging between 100-105 degrees. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... A deep layered ridge across the Southeastern U.S. will prevail through early next week. Surface high pressure will set up across the Northeast, resulting in return flow helping to wrap the deeper Gulf moisture around the backside of the high and into the Deep South. The advection of moisture/instability will support scattered showers and thunderstorms early next week, mainly during the afternoon and evening hours when the sea breeze is active. Temperatures should begin to slightly decrease and trend toward near normal or slightly above normal. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... The terminals are forecast to remain VFR through the 12Z TAF period. A sea breeze is timed to advance across KJZI by 17Z and KCHS and KSAV during the mid to late afternoon. A period of gusty ESE winds should occur in the wake of the sea breeze this afternoon. East winds are forecast to settle between 5 to 10 kts around sunset. Extended Aviation Outlook: Mostly VFR conditions expected; however, isolated convection could bring brief flight restrictions mainly in the afternoon on Thursday and Sunday. && .MARINE... Today and tonight: The marine zones will remain between weak high pressure centered over KY and a wavy stationary front over the western Atlantic. This pattern should provide the region with steady ENE winds, generally between 10 to 15 kts. Seas should remain between 2 to 3 ft. An area of low pressure may develop along the stationary front over the Gulf Stream tonight. Isolated showers and thunderstorms may develop over the coastal waters late tonight. Otherwise, winds will remain from the ENE between 10 to 15 kts with seas between 2 to 3 ft. Late tonight, 4 ft seas may develop across portions of the other GA and Charleston County waters. Thursday through Monday: Thursday will feature a coastal trough/weak low along or near coastal Georgia. Broad high pressure to the north with the weak area of low pressure to the south will result in winds out of the northeast around 10-15 kt. Low pressure could become better defined by Friday before quickly moving out into the Atlantic. Winds will then shift out the south Saturday before settling out of the east Sunday as northerly high pressure returns. Wind speeds will average 10 kt or less over the weekend/early next week with seas 2 to 4 feet. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...BRM LONG TERM...BRM AVIATION...BRM/NED MARINE...BRM/NED