textproduct: Charleston

WHAT HAS CHANGED

Key Message 1 was updated to reflect current observations and ongoing thunderstorms. For Key Message 2, there is increased confidence in mainly dry conditions Friday, as well as morning convection along the immediate coast Saturday, spreading inland through the morning and afternoon. The Aviation Section was updated to reflect the 18Z TAFs.

KEY MESSAGES

- 1) This afternoon will feature scattered thunderstorms across the SC Lowcountry and Southeast Georgia.

- 2) A typical summertime pattern will prevail this weekend into next week. The threat for isolated strong to severe thunderstorms and localized heavy rainfall will exist each day.

DISCUSSION

KEY MESSAGE 1: This afternoon will feature scattered thunderstorms across the SC Lowcountry and Southeast Georgia.

The KCLX radar continues to detect thunderstorms across the region this afternoon, mainly inland of the sea breeze. The KCHS 12Z RAOB Sounding this morning had a PWAT value of 1.9", with mesoanalysis from SPC showing around 2.1" across the region as of 2 PM. Storm motions this afternoon are not overly impressive, however they appear fast enough to limit the heavy rainfall threat. Similar to the past several nights, convection is expected to redevelop over the Atlantic late tonight as low- level convergence shifts back along the west wall of the Gulf Stream after midnight. Activity does not look as extensive as the past few nights, but some degree of isolated to perhaps scattered showers/tstms will make a run for the coast during the early morning hours Friday.

KEY MESSAGE 2: A typical summertime pattern will remain in place through the upcoming weekend. Isolated strong to severe thunderstorms and the threat for localized heavy rainfall will be possible each day.

The pattern will be dominated by deep high pressure over the western Atlantic and Eastern Seaboard. While upper subsidence likely suppresses most convective activity Friday, the pattern will support daily scattered convection each day thereafter. There is increasing confidence that Saturday will begin with morning showers and storms, especially along the GA beaches, with outflow potentially developing new activity north and westward through the late morning and early afternoon Saturday. Then, Sunday and into next week, the sea breeze and any remnant outflow boundaries will serve as the primary focus for afternoon and evening shower and thunderstorm development.

Persistent southerly flow will continue to advect deep moisture into the region. Moderate instability looks to develop each afternoon, with SBCAPE values rising to 2500-3000 J/kg. PWAT values near or slightly above 2 inches each day from Saturday onward will support efficient rainfall rates, with some storms capable of dropping a quick 1-2 inches of rain in a short period. In addition, slow storm motions of around 10 kt, combined with training or repeated rounds of convection, could increase the potential for isolated instances of minor flooding, especially in low-lying and poor drainage areas. Lastly, with little shear in the environment, storms will remain pulse-like. Although widespread severe weather is not expected, a few stronger to marginally severe storms could produce damaging wind gusts.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Prevailing VFR through the 18Z TAFs at KCHS/KJZI/KSAV. Showers and tstorms have pushed inland of the terminals as of 18Z and additional impacts to the terminals this afternoon are unlikely. There is a low chance of some fog development late tonight/early Friday morning, however the current forecast keeps it inland of the terminals. Therefore have not included mention of it in the TAFs at this time.

Extended Aviation Outlook: Periodic flight restrictions are expected in showers and thunderstorms this week and into this weekend.

MARINE

Through Tonight: Generally quiet marine conditions are expected through the remainder of this afternoon as showers and tstorms will likely remain onshore. Another round of showers/tstorms is possible across the marine zones late tonight/early Friday morning.

Friday through Tuesday: Atlantic high pressure will be the dominant synoptic feature through the weekend. Light to moderate winds prevail with gusty winds along the land/sea interface each afternoon associated with the sea breeze. Be alert for the potential for nocturnal jetting to set up Sunday into early next week, keeping breezy conditions in place along the beaches overnight. This feature is typically poorly resolved by models, but the combination of the weak surface trough shifting inland with persistent strong high pressure offshore and very warm water makes for a favorable setup.

CHS WATCHES/WARNINGS/ADVISORIES

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