Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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635 FXUS62 KCHS 052005 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 405 PM EDT Fri Jul 5 2024 .SYNOPSIS... A weak cold front approaching from the west will stall inland this weekend and linger through the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Late this afternoon, KCLX detected a line of weak returns associated with a sea breeze drifting just inland of the coastal counties. Inland of the sea breeze this afternoon and early evening, temperatures should remain in the mid to upper 90s with dewpoints at least in the mid 70s. The combination of the hot temperatures and warm dewpoints will result in widespread heat index values between 105 and 110 degrees. A Heat Advisory will remain in effect for most of the inland counties until 8 PM this evening. A mid-level ridge will remain across the forecast area this evening and tonight. Late this afternoon, visible satellite indicated generally fair weather cumulus across the forecast area. However, two areas of towering cumulus was noted near Lake Moultrie and across the Altamaha River Basin. The forecast will feature SCHC to CHC PoPs for showers and thunderstorms across extreme SE GA. Elsewhere, it appears that an isolated shower or two is possible, but the life cycle would likely remain less than 20 mins. Conditions should steadily stabilize after sunset, resulting in convection to dissipate by late evening. The rest of the night should remain dry with light south winds. Low temperatures are forecast to favor values in the mid to upper 70s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... The upper ridge will be centered over northern Florida on Saturday while a weak shortwave rotates around the northern periphery during the afternoon. A weak cold front is forecast to drop southeast into the area during the day, then stall nearby through early next week. A corridor of extremely high PWATs (2.25-2.5 in, near/above the 99% percentile) is expected to roughly be oriented along and inland of I-95 in the afternoon, between the surface front to the west and the 700 mb ridge axis oriented roughly along the beaches to the east. Weak mid-level subsidence inversion will help convective initiation to hold off until midday to early afternoon, allowing temps to warm into the mid-90s away from the immediate coast. This, in combination with dew points in the mid 70s, will bring heat index values once again to 105-110 degrees away from the beaches, and a Heat Advisory will be needed for tomorrow afternoon. By early afternoon, low level moisture convergence and inland troughing will allow for the initiation of convection along and inland of the sea breeze. Weak flow aloft will bring storm motions only around 10 mph or less, which, combined with the aforementioned elevated PWAT values and CAPE values near 2500 J/kg will bring the potential for a few strong storms inland with locally heavy rainfall (amounts up to 3+ inches) and wet microbursts producing gusty winds the primary concerns into the evening. Convective activity diminishes and shifts inland through the evening Saturday. Sunday and Monday will continue to bring an unsettled pattern as the weak front remains inland and weak disturbances aloft bring periods of enhanced storm chances. POPs generally follow a diurnal pattern, with widespread coverage inland both afternoons, and relatively quieter conditions overnight. Weakening of the upper ridge decreases the threat for dangerous heat, but sufficient instability and moisture remain in place for there to still be at least a limited threat for stronger storms or locally heavy rainfall mainly along and west of I-95 each afternoon. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... A fairly wet pattern likely to persist for much of next week due to deep tropical moisture in place, continual shortwaves, and inland/Piedmont troughing and weak moisture convergence near/east of the weak cold front well inland. The greatest coverage should be during the afternoon and evening hours. Weaker ridging aloft and uncertainty surrounding precip timing and coverage makes the dangerous heat threat more uncertain next week. Additionally, there are no clear signals of any specific day having an elevated severe weather threat, but at least a few stronger storms and some localized heavy rainfall is possible each day through at least mid-week as is normal this time of year. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... Prior to the 18Z TAFs: Visible satellite and sfc observations indicated that a sea breeze was just inland of KJZI, approaching KCHS and KSAV. The sea breeze is expected to pass over KCHS and KSAV during the mid-afternoon hours, shifting winds from the south. Terminals should remain VFR and convection free through tonight. On Saturday, conditions should become unstable early in the day as a front approaches from the west. KSAV TAF will feature a mention of VCSH by 17Z. Extended Aviation Outlook: Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings, this weekend through the middle of next week. && .MARINE... Tonight: The sfc pattern will support south winds between 10 to 15 kts. Seas will favor values around 3 ft, with 2 ft see common within 5 km of shore. Saturday through Wednesday, a typical summertime pattern will persist, with prevailing moderate southerly flow, gusty winds developing near the coast in the afternoon and persisting into the evening/overnight hours, and only modest medium period SE swell keeping seas mainly 2-3 ft. In summary, winds/seas expected to remain below advisory thresholds. Rip Currents: A swell of 2 feet every 9 to 10 seconds and proximity to the new moon will maintain a Moderate Risk for rip currents for Saturday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory until 8 PM EDT this evening for GAZ087-088-099- 100-114-115. SC...Heat Advisory until 8 PM EDT this evening for SCZ040-042>045- 052. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...CEB/JRL LONG TERM...CEB/JRL AVIATION...CEB/JRL/NED MARINE...CEB/JRL/NED