586 FXUS62 KCHS 191401 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1001 AM EDT Mon Jul 19 2021 .SYNOPSIS... The area will remain between Atlantic high pressure and an inland trough through the weekend. && .NEAR TERM /THROUGH TONIGHT/... A warm and very moist environment remains entrenched across the region this morning ahead of a weak stationary front to the west. GOES-E water vapor imagery shows a subtle shortwave west of KATL which is on target to push into the area from the west later this afternoon and evening. As this feature approaches, weak forcing within a very moist and unstable atmosphere should support another round of showers/tstms. However, there is considerable uncertainty on the exact placement and timing of afternoon/evening convection. The various CAMs are offering a number of possible solutions some of which are running about 3-4 hrs apart with the core of the greatest convective coverage occurring as much as 50 miles apart. Much has to do on how quickly the atmosphere destabilizes, where the afternoon sea breeze becomes pinned, how convective outflows interact and when does the corridor of greatest forcing traverse the area. Given the various potential outcomes and uncertainty on exactly how the convective pattern will evolve, pops have been trended down slightly with the core of the highest pops pushed back 1-2 hrs. Modified sounding show the atmosphere will be not be as unstable as yesterday with overall less net MLCAPE. Still, there looks to be plenty of instability with MLCAPE reaching as high as 2500 J/kg by peak heating. Heavy rainfall resulting in urban and minor flooding as well as cloud-to-ground/water lightning look to be the biggest hazards for this afternoon/evening. Localized rain amounts in excess of 3" could occur, especially where convective training develops near any convective outflow and/or sea breeze interactions. Tonight: Convection should develop a ragged outflow boundary, pushing off the coast during the overnight hours. PoPs will trend lower through the night. Low temperatures are forecast to range between 70-75 degrees. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... With the upper trough just to our west and deep moisture in place, Tuesday should again be quite active with numerous showers and tstms, especially in the afternoon and evening. Although the deep moisture sticks around through Thursday, coverage Wednesday and Thursday should be a bit lower due to a slight building in the mid-level ridge and increasing subsidence in a westerly 850 mb flow. Temps will gradually warm during the period. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Fairly typical July weather is in store for the extended period. Atlantic high pressure to the east and a lee trough to the west will keep deep moisture in place and support scattered showers and thunderstorms, mainly during the daytime hours. High temps will be in the lower 90s. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... VFR conditions expected across the terminals this morning. Forecast soundings indicate that conditions across the terminals will become unstable with LFC between 2-3 kft. Showers and thunderstorms are expected to develop and gradually increase in coverage during the mid to late morning hours. A pre-frontal trough is forecast to push over the Coastal Plain this afternoon into the early evening. Numerous to widespread thunderstorms may develop over the coastal counties this PM. The convection will be highlighted with VCSH by 14Z, VCTS by 19Z, and a TEMPO between 21-01Z for 3SM TSRA and gusty winds. Coverage of thunderstorms should remain high through early this evening, then decreasing during the late evening. Extended Aviation Outlook: Brief restrictions from showers and thunderstorms will be possible each day, though the greatest coverage is expected on Tuesday. && .MARINE... Today: A stationary front will remain across the western Carolinas through the near term. A sea breeze is expected to remain pinned to the coast through this afternoon. Winds across the marine zones are forecast to remain from the SW between 10-15 kts with seas between 2- 3 ft. A band of thunderstorms is expected to push over the nearshore waters late this afternoon and evening, advancing to the ENE through the rest of the night. It is possible that thunderstorm clusters could produce swaths of winds of 34 kts or greater and excessive lightning. Tuesday through Saturday: A very typical summertime pattern will persist with Atlantic high pressure to the east and a surface trough over land. Southwest flow with speeds mostly 15 knots or less will persist. A sea breeze will develop each afternoon along the coast. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$