Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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836 FXUS62 KCHS 190522 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 122 AM EDT Thu Sep 19 2024 .SYNOPSIS... Weak high pressure will develop over the region on Thursday. The area of high pressure is expected to gradually strengthen through early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Mid-level circulation center is now across the mid-Atlantic region with drier mid level air wrapping around the western and southern side down through Georgia. Earlier shower activity has pretty much ended and leftover debris cloud continues to slowly fade in time. Quiet weather is anticipated through the balance of the night. That said, recent CAM guidance solutions want to kick off some additional shower activity overnight in the tri- county vicinity into the Atlantic. Discounting that idea for now. Meanwhile, with clearing skies, light/calm winds...risk for fog and stratus will increase particularly where there was decent rainfall Wednesday afternoon (essentially along the I-95 corridor). HREF highest fog probabilities favor southeast Georgia, especially south of I-16 where strongest drying aloft/clearing skies will be found. A Dense Fog Advisory is certainly possible toward morning. Lows tonight will range from the mid-upper 60s inland to the lower 70s at the beaches and Downtown Charleston. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... Thursday: Short term guidance indicates that the forecast area will remain under a broad H5 longwave trough. At the sfc, a weak ridge should build across the western and central Carolinas as a broad trough remains over the Coastal Plain. As temperatures warm into the mid to upper 80s, a very weak sea sea breeze is forecast to develop during the early afternoon, but should remain over the coastal counties through late afternoon. There should be enough instability during the heat of the afternoon to support isolated to scattered showers with isolated thunderstorms along the coast. Any convection should dissipated by the mid-evening hours. Friday: The axis of the mid-level trough should ripple east over the western Atlantic as strong ridge centered over TX starts to build east. GFS indicates that a short wave is expected to track from north to south across the forecast area during the afternoon. As temperatures reach the mid to upper 80s over dewpoints in the 70s, weak instability should develop across the region. The combination of the shortwave passage and weak instability may support isolated convection along the coast during the afternoon. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Saturday and Sunday: The forecast area will become dominated by weak sfc high pressure as a H5 ridge builds across the Deep South and Southeast U.S. Forecast soundings indicate that the environment will remain generally dry with a significant inversion at H75. The forecast will indicate dry conditions each day. High temperatures should favor values in the upper 80s, with low 90s possible across inland GA on Sunday. Monday through Wednesday: Long term guidance indicates that the H5 ridge will shift east across the northern Gulf coast and FL. H5 heights should increase across the forecast area, limiting any instability across the forecast area. The forecast will feature dry weather through early next week. High temperatures are forecast to remain in the mid to upper 80s on Monday, then mid 80s expected through the rest of the forecast period. && .AVIATION /05Z THURSDAY THROUGH MONDAY/... 19/06z TAF Discussion: KCHS/KSAV/KJZI: There is a risk for fog and stratus development overnight as wet grounds from earlier rainfall combine with clearing skies and light winds. The best fog/stratus parameters look to occur across interior Southeast Georgia where KSAV will likely be on the eastern periphery of the lowest vsbys. For now, cigs were limited to MVFR with a TEMPO group from 10-13z for IFR cigs just above alternate minimums with MVFR vsbys. Lower conditions are possible with amendments likely toward morning. For KCHS, fog/stratus looks a bit more marginal although it is located close to where heavier rains fell earlier. VFR was maintained, but with a TEMPO group for MVFR cigs with scattered clouds at 600 ft between 10-13z. Light MVFR fog was also included between 10z-13z. At KJZI, VFR was continued as fog/stratus looks to remain west of the terminal. Some light fog could occur as winds go light and skies clear, but no meaningful reductions in vsbys are expected at this time. Extended Aviation Outlook: VFR. No significant weather expected. && .MARINE... Tonight: Southerly flow early evening will veer to the west and northwest late tonight towards daybreak. Speeds generally remain less than 10 knots with seas 1 to 3 ft nearshore waters out 20 NM and 3-4 feet over the Georgia offshore waters out 20-60 NM. Thursday through Sunday: Building high pressure should result in winds between 10-15 kts with sea generally between 2-4 ft. No headlines expected during this period. && .TIDES/COASTAL FLOODING... Positive tidal anomalies along with high astronomical tides from the full moon will lead to elevated tides for the rest of this week and through the weekend. Coastal Flood Advisories will probably be needed for both the morning and evening high tides through Friday for both Charleston Harbor and Fort Pulaski. The astronomical high tides start to lower Saturday and Sunday, but the morning high tides will likely be elevated enough to still require Coastal Flood Advisories (especially for Charleston and coastal Colleton Counties). More uncertainty exists for Fort Pulaski. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$