Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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293 FXUS62 KCHS 121849 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 249 PM 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 /UNTIL 6 PM THIS EVENING/... No significant changes with the late morning update as mainly sunny skies prevail north of the Altamaha River region and temps are warming into the lower to mid 80s for most as of 11 AM. 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 /6 PM THIS EVENING 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 WEDNESDAY/... 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 /19Z WEDNESDAY THROUGH MONDAY/... VFR prevails at all terminals through the TAF period. More robust low level moisture could make a push toward the coast around daybreak Monday morning as low pressure develops within coastal troughing off the Southeast coast, but any sub-VFR ceilings are unlikely to progress any further inland than the beaches through at least the morning hours. Scattered mid and high clouds overnight preclude any significant fog threat, with gusty E winds this afternoon diminishing as the sea breeze circulation fades this evening. Extended Aviation Outlook: Mostly VFR conditions expected; however, isolated convection could bring brief flight restrictions mainly in the afternoon on Thursday and Sunday. && .MARINE... Tonight: Breezy conditions near the coast this afternoon will diminish as the sea breeze circulation weakens early this evening. Moderate northeast winds then prevail tonight as low pressure begins to gradually deepen off the Southeast coast. Isolated showers and thunderstorms may develop over the coastal waters late tonight. Seas increase a bit to 2-4 ft overnight with increasing ENE windswell, with an underlying modest medium period S to SE swell continuing as well. 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/CEB LONG TERM...BRM AVIATION...BRM/CEB MARINE...BRM/CEB