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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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372 FXUS62 KCHS 140248 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1048 PM EDT Tue Aug 13 2024 .SYNOPSIS... A cold front will move slowly south across the area tonight, then pass through on Wednesday. High pressure will build from the north into late week. Another cold front may approach the area later this weekend or early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Tonight: Aloft, a broad trough extends across the Northeast and Mid- Atlantic states, placing the Southeast along it`s southern edge. At the sfc, a front will continue to slowly nudge south across Southeast Georgia overnight, potentially departing the local area within the next few hours. Most areas will remain rain-free through the remainder of the night as the atmosphere has been worked over from convection experienced earlier. Late tonight, there could be some shallow ground fog around, especially in areas that received rain earlier this afternoon into the evening, but coverage isn`t expected to be sufficient to warrant carrying fog in the forecast. Lows are expected to be a bit lower than previous nights, generally in the low-mid 70s inland to upper 70s near the beaches. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... Wednesday: This will be the wettest day to an otherwise rather unusually dry period. A weak backdoor surface front will be pushing just south of the area by later in the morning, with surface ridging building over the mid Atlantic and northeast states, resulting in northeast low level northeast winds. The area will still be under the backside of an upper level trough, departing off of the mid Atlantic Coast. This feature, combined with modest deep layer moisture of PWs of 2+ inches, will result in scattered showers/thunderstorms, especially south of the Charleston Tri-County area. Highs noticeably cooler over the SC zones, in the mid to upper 80s, and around 90 to the lower 90s southern GA zones and near the Altamaha. Expect any isolated to scattered convection to diminish by the evening. Lows cooler than they have been in quite some time, in the upper 60s to around 70 inland, and lower to mid 70s near the coast. Thursday and Friday: Deep layer ridging shown by all models to build from the west and north, helping to drive drier air southward through the area. PWs falling below 1.5 inches and mean RH values generally below 50%, which is below normal for this time of year. Have no mentionable precipitation chances for both of these days, which will allow for some needed drying out of the many flooded/saturated regions across our area. Highs a tad below normal, in the mid 80s to near 90. Lows in the upper 60s inland/west of I-95 and lower 70s closer to the coast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The deep layer ridging over the southeast U.S. is shown by global models to weaken and push southward as a large/broad upper trough forms over the Great Lakes Saturday, pushing into southeast Canada and northern New England Sunday and Monday. This will translate to a gradual increase in precip./convection chances through the period. Have slight chance PoPs Saturday and into Sunday, then chance by Monday, which is around normal for this time of the year. Given the presence of a relatively strong upper level trough axis for mid August, will continue to monitor any potential threat for strong to severe storms, especially by later in the weekend. Temperatures warming slightly through the period, but guidance keeps highs around normal in the lower 90s and lows in the lower to mid 70s, except mid to upper 70s near the coast. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... VFR conditions are expected at CHS/JZI/SAV terminals through 00Z Thursday. However, there is a chance of MVFR conditions late tonight due to some low clouds attempting to develop at all terminals, and again with showers/thunderstorms near a slowly moving front, mainly at the SAV terminal Wednesday afternoon. Confidence remains too low to include flight restrictions at the terminals, but amendments could be needed to address the issue during the next 24 hours. Extended Aviation Outlook: Wednesday: Brief flight restrictions possible with scattered mainly afternoon and early evening showers and thunderstorms, especially KSAV. Thursday and Friday: VFR to prevail with much drier conditions expected, with less than 15% chance for afternoon showers/thunderstorms. Saturday and Sunday: Some moisture starts to return with isolated afternoon showers/thunderstorms Saturday, and scattered by Sunday with a higher chance for brief flight restrictions. && .MARINE... Tonight: A few thunderstorms will continue to shift further offshore and south along a boundary, likely departing all local waters within the next couple hours. An isolated strong thunderstorm is possible, with gusty winds and perhaps even a waterspout. Otherwise, a weak boundary will linger near or just south of the local waters through the night. Winds north of the boundary will turn northeasterly while winds to the south will continue to be southerly. Speeds should top out in the 10-15 knot range, mainly within the northeast flow in the Charleston County waters. Seas are expected to average 2-3 feet. Wednesday through Thursday: No highlights expected as a backdoor cold front pushes south of the waters through this period. Expect east-northeast winds of 10-15 knots with some gusts to near 20 knots possible. Seas generally 3 to 4 feet. Thursday night through Saturday: Seas expected to increase, especially beyond 20nm offshore as swells from Ernesto, which will remain well east of the area, arrive into the marine area. Guidance indicating seas building to 4 to 6 feet, possibly up to 7 feet by later Friday and into Saturday. Decreasing northeast winds through Friday, becoming south and southwest Saturday and Sunday. Winds during this period generally 10 to 15 knots or less and seas 3 to 5 feet. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...DPB SHORT TERM...RFM LONG TERM...RFM AVIATION...DPB/RFM MARINE...DPB/RFM