Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
800 FXUS62 KCHS 161111 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 711 AM EDT Wed Jul 16 2025 .SYNOPSIS... Atlantic high pressure will prevail through early next week. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, the east to west oriented ridge axis will continue to extend into the GA/SC coast. At the surface, The subtropical high will be the primary feature and will drive the low-level flow pattern across the forecast area. Overall, today does not look particularly active for convection. The ridge aloft will help to keep coverage down, and model soundings are rather warm and only depict MLCAPE values of up to around 1,500 J/kg. Instead, we will likely continue to see weak convection push onshore from the coastal waters within the onshore flow throughout much of the day. Any diurnal land-based convection that develops also looks to be weak and not a severe threat. Also, the locally heavy rain threat is low thanks to the progressive nature of this convection with storm motion on the order of 15-20 mph. Temperatures are forecast to top out in the low 90s, with heat indices mostly in the low 100`s and some isolated values into the mid 100`s. Tonight: Overall, little change to the pattern overnight. Any lingering land-based convection should dissipate through the early evening, though there will still likely be some shower activity over the coastal waters trying to push onshore at times. The low-level flow will start to become more south- southwest or southwest with time which should keep most of the nocturnal convection across the coastal waters off the coast. Similar lows to the last few nights, with temperatures falling into the low to mid 70s inland and hanging around in the upper 70s along the coast. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... A strong deep layered ridge will prevail Thursday through Saturday, bringing hot and humid conditions. Friday and Saturday will feature highs in the mid/upper 90s, dewpoints in the mid/upper 70s, and heat indices topping 108 in some places. We could need Heat Advisories for part of the area both days. An increase in upper level subsidence will limit PoPs to 20-30%. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... The upper ridge axis will shift west of the area late in the weekend into early next week, allowing some shortwave energy to rotate in from the north. This could result in an increase in diurnal convection coverage Monday and Tuesday. Toasty conditions will continue into Monday, with possible Heat Advisories both days. Temps may cool slightly by Tuesday. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... The 12z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. The primary issue this morning will center on showers streaming onshore and producing brief periods of MVFR ceilings and visibilities. Chances will be highest at KCHS and KJZI through about midday and we have maintained the TEMPO groups there. KSAV is in the clear for morning showers, but could potentially see isolated showers and storms this afternoon. However, chances are too high to include in the TAF. Winds will be stronger today, with frequent southerly gusts into the 15-20 knot range. 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: Subtropical high pressure to the east will be the primary feature driving the flow across the local waters through the period. Winds today will be southerly with speeds mostly in the 10-15 knot range, though there could be an occasional 20 knot gust. Overnight, winds will slightly start to veer around to become more south-southwest late. Speeds should be the same, mostly 10-15 knots with occasional gusts up to 20 knots. Seas should average 3-4 feet through the period. We will likely continue to see isolated to scattered showers and thunderstorms across the coastal waters today within the onshore flow. This activity isn`t expected to be particularly strong and there is a low probability of strong wind gusts. High pressure will prevail Thursday through Monday, maintaining typical summertime weather in the marine area. No headlines expected. && .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