Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
441 FXUS62 KCHS 130548 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 148 AM EDT Sun Jul 13 2025 .SYNOPSIS... Weak high pressure will continue to build across the region through the week. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, the center of the upper ridge will be situated just off to the southwest of the forecast area with the ridge axis extending up through north GA and into the Southern Appalachians. At the surface, the forecast area will be situated within a baggy trough that extends from a surface low positioned off the Mid Atlantic coast. This setup will actually provide northwest to north flow through the column today, yielding an uncommon storm motion of north to south. Concerning thunderstorms, model guidance again suggests that coverage won`t be overwhelming but the same threats apply as the last few days. The setup featuring northwest surface flow should work to keep the sea breeze pinned closer to the coast in the afternoon, meaning that convective initiation should favor the immediate coastline as well. In fact, there is some agreement that convection will initiate generally across eastern Berkeley and Charleston counties in the early to mid afternoon, push to the south, and also throw out outflow boundaries that will move to the south and southwest and drive additional development down the coastline into the early evening hours. The area along and east of I- 95 will remain within a slot of deep moisture and precipitable water values of 2-2.2 inches. Warm and moist profiles will again yield a rather modest severe environment, with the main threat being wet microbursts that occur in conjunction with the best boundary interactions. The heavy rain threat remains the same as well, where locations directly impacted by thunderstorms could see 1-2 inches of rain. It will also be a warm and humid day with high temperatures expected to top out in the mid to upper 90s for much of the area. The highest dewpoints are expected to be generally along and east of I-95, peaking in the mid to upper 70s. This should yield heat index values on the order of 100-105 degrees, just below Heat Advisory criteria. Another limiting factor should be the development of thunderstorms in the early to mid afternoon which will disrupt peak heating for portions of the area. Tonight: The best coverage of showers and thunderstorms should shift down the coast and into southeast Georgia through the early to mid evening hours. Some convection could linger into the early morning hours depending on how outflow boundaries progress. But overall, land areas should be dry late in the overnight while the coastal waters become more active. Otherwise, a pretty standard summer night with lows only in the mid 70s for much of the area. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... A weak upper level ridge will remain over the Southeast Monday into Tuesday before weakening. Meanwhile Bermuda high pressure will prevail at the surface. A relatively typical July pattern will continue, albeit with slightly greater diurnal convective coverage. Deep moisture and moderate instability will support locally heavy rainfall with any shower or thunderstorm that develops, and isolated severe thunderstorms are also possible. Above normal temperatures expected Monday, particularly far inland where highs will climb into the upper 90s. Near-normal highs expected Tuesday and Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... A deep layered ridge will develop over the Southeast late week into the weekend, producing typical summertime weather. Ample moisture and instability should allow scattered convection each day, primarily seabreeze-driven. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... The 06z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. There could be an area of low stratus that develops across interior southeast SC closer to sunrise and there is a chance it builds into KCHS. For now we think it will stay just inland, and we have kept the forecast VFR. Otherwise, the main concern for the TAF period will be thunderstorms later this afternoon and evening. We have maintained the TEMPO groups at all 3 sites, starting at 20z at KCHS, 21z at KJZI, and 22z at KSAV. Heavy rain and gusty winds will be the main threats, possibly producing a brief period of MVFR or IFR conditions. Extended Aviation Outlook: VFR will mainly prevail throughout the period, however brief flight restrictions are possible within showers and thunderstorms that develop in the afternoon and/or evening hours. && .MARINE... Today and tonight: Overall, continued quiet and well below Small Craft Advisory conditions for the local waters. West- northwest or northwest winds this morning will be quite weak, with speeds topping out 5-10 knots. For the afternoon and evening, winds will flip around to become southerly under the influence of the sea breeze circulation with speeds still mostly 10 knots or less. Right along the land/sea interface speeds could top out in the 10-15 knot range, including Charleston Harbor. Then overnight, winds will continue to be quite weak, diminishing to less than 10 knots. Seas should average around 2 feet, but could be up to 3 feet around the 20 nm line and beyond. Much like the last few days, thunderstorms are expected to develop along or just inland of the coast and then move southward to the coast or out over the coastal waters. Frequent lightning and strong wind gusts will be the primary threats. A persistent southerly flow will continue over the waters Monday through Thursday as high pressure sits offshore. A moderate sea breeze will develop each afternoon, with wind gusts in Charleston Harbor occasionally topping 20 kt. No headlines currently anticipated. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM...JRL LONG TERM...JRL AVIATION...BSH/JRL MARINE...BSH/JRL