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Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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421 FXUS62 KCHS 121444 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1044 AM EDT Mon Aug 12 2024 .SYNOPSIS... A stationary front will remain just to the west through Tuesday before dissipating. Weak high pressure will build in from the north during the middle of the week and prevail into the latter part of the week. && .NEAR TERM /THROUGH TONIGHT/... Late this morning: Surface analysis continues to reveal a weak front situated to the west and north of the forecast area. We start the day with mostly clear skies and plenty of sun, which is allowing temperatures to rise into the upper 80s already. Concerning convection chances this afternoon, it appears the best instability will reside across our southeast South Carolina counties and down along the Georgia coast. Guidance suggests that some lower dew points will filter in across interior southeast Georgia which will lower the thunderstorm risk there. Hi-res models continue to highlight Colleton County through the Tri-County region, inland of the coast. This area will be situated near the aforementioned front as well as the afternoon sea breeze. With DCAPE values progged to be around 1,000 J/kg, a severe threat will exist for damaging wind gusts. However, no organized severe weather is expected as the stronger storms will likely occur where more significant boundary interactions occur. With highs in the low to mid 90s and dew points in the mid to upper 70s along the Georgia coast up through Beaufort and Jasper counties, heat index values are still forecast to reach 108-110 degrees. Therefore, the Heat Advisory remains in effect. We could see isolated locations get up to near 108 in the Tri- County region, but the Heat Advisory risk is much more marginal there. Tonight: Convection will diminish through the evening hours with quiet conditions overnight. Lows will dip back into the upper 70s to around 80. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: A weak surface front and area of low pressure across the Midlands will meander across the area through the day. A trough across the Northeast and Mid-Atlantic states will dig into the Southeast late which will push those surface features southward. Low-level convergence near the front, in addition to the sea breeze, will be enough to support at least scattered showers and thunderstorms during the afternoon and evening. Guidance favors southeast South Carolina for the greatest coverage with conflicting coverage across southeast Georgia. The forecast reflects at least slight chance POPs across our southern zones considering PWATs in that area will be around 1.7 inches. With plenty of instability, we can`t rule out a stronger storm or two, especially where boundary interactions occur. However, the overall severe threat will be low. Also, some storms could produce locally heavy rainfall. Given that ground conditions are wet and some areas are still experiencing flooding, there is little to no tolerance for additional rainfall. Therefore, any thunderstorm that develops will have the potential to quickly produce flooding issues. High temperatures are forecast to reach the low to mid 90s and overnight lows will be in the low to mid 70s away from the coast. Wednesday: A trough across the Northeast and Mid-Atlantic states will continue to dig into the Southeast, helping to nudge the aforementioned weak front offshore. Models suggest a very narrow swath of deep moisture passing over the area associated with the front, in addition to upper forcing, which will again bring at least scattered convection during the afternoon/evening hours. Wednesday will be touch cooler with highs in the upper 80s across our southeast South Carolina counties and low 90s for our southeast Georgia counties. Min temps will largely bottom out in the low to mid 70s with some inland spots in the upper 60s. Thursday: Weak high pressure will begin to build in from the north, along with relatively drier and cooler conditions. This will keep rain chances to a minimum. The current forecast features slight chance to chance POPs, which may even be overdone. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Weak high pressure will linger for a day or two before a cold front quickly approaches. This will result in lesser chances of diurnal convection during the weekend. The front could pass over the forecast area early next week, which could lead to higher rain chances. Temperatures should rise a degree or so each day with highs back into the low 90s this weekend, around near- normal for this time of year. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... Isolated to scattered showers and thunderstorms are possible again this afternoon along the sea breeze with high-res guidance suggesting the higher precip chances will be at CHS. 12Z terminal forecasts will include VCSH for the CHS terminal after 19Z. No mention for JZI and SAV for now. Any showers/storms will diminish through the evening hours with VFR conditions persisting overnight. Extended Aviation Outlook: Brief flight restrictions are possible in afternoon and evening showers/thunderstorms through the period. && .MARINE... Today: Southwest winds continue across the coastal waters today with winds trending a bit more southerly this afternoon with the sea breeze. Sustained winds of 10 to 15 kts with some higher gusts. Seas should generally range between 2 to 3 ft in a mix of southeasterly medium period swell and southerly wind chop. Tuesday through Saturday: A deep offshore ridge will result in southwest flow around 10 kt or less Tuesday. Wednesday afternoon, high pressure will begin gradually build in from the north after a weak front departs southward which will cause winds to shift out of the northeast. Seas will average 2-3 feet; however, by the end of the week seas will start to rise as increasing swell arrives from what could be a strengthening tropical system over the open Atlantic. Small Craft Advisories could be needed for a portion of the marine zones for 6 ft seas. && .HYDROLOGY... Most of southeast Georgia and southeast South Carolina remains quite vulnerable to additional rainfall following the 10-20 inches of rain that fell last week. Many areas are still experiencing ongoing flooding, and any additional rainfall from thunderstorms will certainly not help conditions improve. Scattered to numerous thunderstorms are forecast each afternoon and evening through midweek, and any locally heavy rainfall could produce new areas of flooding. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory until 6 PM EDT this evening for GAZ116>119- 137>141. SC...Heat Advisory until 6 PM EDT this evening for SCZ047>049-051. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...NED