textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Strong to severe thunderstorms are possible today and Tuesday.

- 2) Unsettled weather with the potential for locally heavy rainfall continues mid to late this week.

DISCUSSION

KEY MESSAGE 1: Strong to severe thunderstorms are possible today and Tuesday.

Recent SPC mesoanalysis indicated between 3000-4000 J/kg of MLCAPE, LI as low as -7, and low level lapse rates around 8 C across the coastal counties. In addition, DCAPE values were in excess of 1300 J/kg across the entire forecast area. Strong updrafts should materialize along and ahead of the sea breeze this PM. Given weak effective shear, these storms may remain pulse-like and storm motions around 10 kts. A couple of storms may develop strong to severe wind gusts below collapsing updrafts, with Special Weather Statements and Severe Thunderstorm Warnings possible. The forecast will indicate scattered to numerous PoPs along the sea breeze, near the coast, with little to no mentionable PoPs across inland GA/SC. Convection should decrease this evening, not only with the loss of heating, but storms should cross over the sea breeze into elevated instability.

On Tuesday, conditions should change very little from today. However, the weak boundary inland should make some progress closer to the coast. This boundary in addition to the sea breeze may increase llvl moisture convergence, especially across SE GA. Scattered to numerous thunderstorms should develop during the heat of the afternoon. Given similar thermal profiles on Tuesday, one or two severe thunderstorms are possible.

KEY MESSAGE 2: Unsettled weather with the potential for locally heavy rainfall continues mid to late this week.

The mid-levels will consist of troughing over the eastern half of the U.S. midweek, followed by it shifting over the East Coast by the end of the week. Additionally, a series of shortwaves embedded within the trough will pass over our region. At the surface, a stationary front will be spread across or in the vicinity of our area mid to late this week. There will be deeper moisture along and south of the front, with PWATs ~2". These values are above normal for this time of year. The combination of regional and mesoscale lift along with the moisture will generate rounds of convection each afternoon and evening mid to late this week. The models are generally in good agreement on the convective coverage. But the day to day timing and locations of the stronger convection will need to be refined with future forecasts. The threat for widespread and organized severe thunderstorms looks low. But since it's summer, we cannot rule out stronger to marginally severe storms each day with damaging winds. But the main concern appears to be the heavy rainfall potential. If the storms are slow moving, train, or backbuild, then quite a bit of rain could fall, which could lead to localized flooding. WPC is highlighting our area in the ERO to account for this. Once again, the details will need to be refined with future forecasts.

AVIATION /18Z MONDAY THROUGH SATURDAY/

18Z TAFs: Moderate instability will remain across the terminals this afternoon into early this evening. Storm coverage will likely remain the greatest near the sea breeze this afternoon, highlighted with TEMPOs at each terminal. Storms could linger until sunset, then convection should gradually diminish with the loss of heating. Once the storms dissipate, the rest of the TAF period should remain dry with light winds.

Extended Aviation Outlook: Showers and thunderstorms could bring brief flight restrictions each afternoon.

MARINE

Tonight: The pressure pattern will generally support southwest winds between 10 to 15 kts across the marine zones. Wave heights are forecast to remain between 2 to 3 ft. The primary concern will be sea breeze triggered thunderstorms drifting over the nearshore waters this afternoon into early this evening. Some of these storms may produce strong wind gusts along with cloud to surface lightning.

Rest of this week: South to southwest winds will persist through the period. Conditions will remain below Small Craft Advisory levels, with winds averaging 15 knots or less and seas 2 to 3 feet. Any showers or thunderstorms that move over the waters have the potential to bring higher wind gusts and frequent lightning.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.