Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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310 FXUS62 KCHS 301721 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 121 PM EDT Tue Apr 30 2024 .SYNOPSIS... High pressure will prevail through much of the week. A weak disturbance will move through today and Wednesday, then a weak cold front will stall in the vicinity this weekend. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: Aloft, a mid-upper level ridge will be forced further offshore as h5 shortwave energy progresses eastward across the Southeast United States. At the sfc, a lee trough will develop across the Midlands/Upstate while the local area remains along the western fringes of Atlantic high pressure. The pattern will result in mainly dry conditions for the next few hours, before h5 shortwave energy arrives late afternoon. A southerly sfc wind will advect greater moisture across the region (PWATs 1.25-1.50 inches) while ample sfc heating under thin cirrus leads to afternoon highs in the low-mid 80s away from the beaches. Instability remains modest mid afternoon, but a few showers can not be ruled out near the vicinity of a seabreeze circulation moving inland. By late afternoon, greater precip chances arrive across far inland locations, where greatest moisture/instability aligns with h5 shortwave energy approaching from the west. Convection should remain somewhat disorganized given modest CAPE and bulk shear. However, a few stronger thunderstorms can not be ruled out well inland when forcing and moisture convergence becomes enhanced as the shortwave encounters the local seabreeze by early evening. Gusty winds and small hail will be the main concerns should a stronger thunderstorm occur. The highest chances for convection should remain along and west of I-95, where 30-45% PoPs remain in the forecast. Tonight: The h5 shortwave passes through the forecast area, reaching near the coast or offshore by Wednesday morning. The lee trough remains in place, while the western side of the Atlantic ridge pulls a bit further out to sea. There is just enough instability and ample moisture for the shortwave to work with, so chance PoPs remain for much of the night. Although with the passage of the shortwave, probabilities drop off across Georgia late. The nocturnal environment is not conducive for severe storms after the early evening. There are indications of some fog forming across parts of Georgia after midnight. But with perhaps too much lingering cloud cover, we refrained from including in the forecast at this time. Given the cloud cover, overnight lows should be more mild than previous nights, generally in the lower 60s inland to mid-upper 60s closer to the coast. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... A few showers could move through the Charleston Tri-County area Wednesday morning in association with the tail end of the upper shortwave. Weak upper level subsidence will develop during the afternoon as shortwave ridging occurs. However, moderate moisture will remain in place during the afternoon, and a decent sea breeze will develop, potentially popping isolated showers. Deep layered ridging Thursday into Friday should maintain dry weather with above normal temperatures. A shortwave could approach far western areas late Friday afternoon so it`s possible some convection could drift into those zones late in the day. Highs will reach the mid to upper 80s both days. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A relatively zonal flow will develop Friday night and continue into early next week, with occasional shortwaves rippling through. A weak cold front is forecast to stall across far inland areas over the weekend. Tropical moisture will spread into the area with PWATs hovering around 1.7" much of the period. Isolated to scattered mainly diurnal convection is expected, along with above normal temperatures. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/... KCHS/KJZI/KSAV: VFR will prevail at all sites through 12Z Wednesday. There will be a few showers off the coast of KJZI during the late morning and early afternoon, as they remain offshore. Upstream from all terminals, scattered SHRA/TSRA will occur during the mid and late afternoon, eventually progressing east tonight. While flight restrictions are possible should any directly impact a terminal, probabilities are too low to show anything in the latest TAFs. All airfields will experience some wind gusts of 15-20 kt in wake of the sea breeze after 18-19Z. Extended Aviation Outlook: VFR will generally prevail. && .MARINE... This Afternoon and Tonight: High pressure centered across the western Atlantic will extend toward the Southeast Coast while a trough remains inland. The pattern will favor a southerly sfc wind around 15 kt or less across all local waters with the exception of the Charleston Harbor this afternoon, where 20 kt gusts are possible near a seabreeze circulation developing, then shifting inland. Seas will range between 2-4 ft, largest across offshore Georgia waters. Mariners should remain alert for thunderstorms later today, but mainly this evening and/or tonight, with a few potentially resulting in gusty winds and frequent lightning strikes. Wednesday through Sunday, no marine concerns expected. Atlantic high pressure will remain the dominant feature with a relatively weak gradient in the area. Wind speeds will generally stay below 10 kt except right along the coast in the afternoon sea breeze, and seas will mostly run 2-3 ft. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...DPB SHORT TERM...JRL LONG TERM...JRL AVIATION... MARINE...DPB