FXUS62 KCHS 032345 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 745 PM EDT Tue Aug 3 2021 .SYNOPSIS... A stalled front will linger over or near the area through the week with a threat for heavy rainfall. More typical summertime weather should then return early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Early this evening: Surface analysis yields a complex setup across the forecast area. A weak area of low pressure currently sits across much of southeast Georgia and the adjacent coastal waters while a wedging high builds in from he north, centered across the Mid-Atlantic states. A weak surface front is draped along the coast and matches up well with where ongoing convection is currently configured. Inland of the front, the airmass continues to stabilize as evidence by MLCAPE well below 500 J/kg. The only real available instability at this juncture runs from around Beaufort County, southwestward across Chatham, Bryan, Liberty, Long, and McIntosh counties. This is the area where thunderstorms will still be possible through the evening and as such we have trimmed the Flash Flood Watch to only include this region. Additional rainfall amounts of up to 2 inches will be possible within the watch area through late evening. Elsewhere, most of the area will be rain-free, though light rain will linger across portions of Charleston and Colleton counties for a few more hours. After midnight, the focus for thunderstorm development will shift offshore as the low moves off the coast and northerly low-level flow fills in across the forecast area. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... Forecast confidence: Moderate overall; low for rain chances, amounts, and timing. A stalled weak surface front/trough will persist over or just northwest of the area while upper troughing lingers over the region into early Thursday before lifting out. The main concern is the risk for localized flash flooding, mainly closer to the coast closer to the deepest moisture/instability. Temperatures will likely stay near to below normal through the period. Wednesday: Latest model guidance suggests drier conditions than the previous forecast behind a wave of low pressure departing off to the northeast early in the day so we have lowered rain chances/amounts. Another wave could impact the area Wednesday night bringing a better chance for some heavy rain especially to coastal areas. Thursday: Similar trend as Wednesday as models aren't too aggressive regarding rain coverage/amounts during the day as the upper trough and a possible surface wave shifts off to the northeast. Another wave/surge of moisture could impact the area Thursday night. Locally heavy rainfall/flooding will be possible. Overall, the best chances/amounts appear most likely near the SC coast and in GA. Friday: Looks like some mid-level ridging tries to hang on while a deep upper trough near the MS Valley tries to shift east. The best rain chances look to be near the coast earlier in the day and then potentially shift inland near the surface trough and upper forcing later in the day. Localized flooding will once again be possible, but could largely depend on how much/where the heavier rain falls over the previous few days. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Forecast confidence: Moderate. Deep troughing is likely to generally prevail through at least Saturday with the most unsettled conditions through then given that is when the best moisture/forcing are expected. Conditions should become more typical of summer thereafter through early next week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... This evening, the best chance for direct impacts from thunderstorms will be at KSAV. Still think that thunder will stay south of the terminal so it is not explicitly mentioned in the TAF at this time. The coverage of showers and thunderstorms will diminish quickly after midnight and then attention turns to the arrival of widespread MVFR and IFR stratus. Model guidance is quite consistent in bringing in IFR ceilings to KCHS, KJZI, and KSAV by the early morning hours and keeping it around through around midday. This is what the forecast follows, showing improvement at all three sites around 16z to MVFR, and then VFR by the early afternoon. The chance for afternoon thunderstorms has lowered on Wednesday and the forecast does not explicitly mention anything at this time. Extended Aviation Outlook: Mainly VFR through Saturday. Potential for periodic restrictions from showers and thunderstorms, as well as morning low clouds and fog. && .MARINE... Through Tonight: A surface low pressure has formed off the Georgia coast and will continue to move northward through the period. West to southwesterly winds will prevail, generally 10 to 15 knots with seas 2 to 4 feet. Higher wind gusts and seas are possible in or around any thunderstorms. Shower and thunderstorm activity should gradually decrease near shore, however showers and thunderstorms may persist through daybreak near the Gulf Stream. Wednesday through Sunday: Moderate confidence this period. Atlantic high pressure along with an inland stalled front/trough will prevail through the period. Winds could briefly get near Small Craft Advisory levels at times across a portion of the southern SC/northern GA coastal waters but confidence is low in the need/timing for any headlines at this time. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Flash Flood Watch until midnight EDT tonight for GAZ116>119- 137>141. SC...Flash Flood Watch until midnight EDT tonight for SCZ048-051. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM...RJB LONG TERM...RJB AVIATION...BSH MARINE...CPM/RJB