textproduct: Charleston

WHAT HAS CHANGED

All Key Messages and Sections were updated.

KEY MESSAGES

- 1) Another round of showers and thunderstorms will be possible inland this afternoon ahead of an advancing sea breeze.

- 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.

DISCUSSION

KEY MESSAGE 1: Another round of showers and thunderstorms will be possible inland this afternoon ahead of an advancing sea breeze.

This Afternoon and Tonight: Renewed chances for isolated to scattered showers/storms will be possible again ahead of an advancing sea breeze. However, unlike this morning, should see most of the activity develop inland rather than along the coast. As noted in the previous discussion, overall forcing remains rather meager, suggesting that development will be airmass induced and driven by mesoscale processes. Though we are currently not outlooked in SPC's latest Day 1 Severe Risk, do want to point out that an isolated storm could still become strong to severe this evening, with damaging winds being the primary hazard.

Activity will quickly wane this evening, but there are increasing signals that another round of noctural convection could develop over the Atlantic overnight as low-level convergence refocuses closer to the west wall of the Gulf Stream. Latest models suggest that areas along/east of the I-95 corridor would be favored by early Thursday morning. Like today, could see bouts of heavy rainfall and localized flooding occur, especially in urban or low-lying areas with poor drainage.

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

The pattern aloft will be dominated by deep high pressure over the western Atlantic and the western CONUS through the weekend. This will support daily scattered convection, with the sea breeze and any remnant outflow boundaries serving as the primary focus for afternoon and evening thunderstorm development. Persistent southerly flow will continue to advect deep moisture into the region with PWATs near 2 inches and SBCAPE values as high as 3000 J/kg. These parameters 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. Friday could be the exception, as somewhat drier air with pockets of PWATs around 1.5 to 1.7 inches should limit the flooding threat. Lastly, with little shear in the environment, storms will remain pulse-like. Although widespread severe weather is not expected, a few stronger storms could produce damaging wind gusts.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

18Z TAFs: Latest radar imagery shows a few lingering showers/storms near KCHS/KJZI, as a sea breeze develops further south. Outside of some brief reductions in cigs/vsbys should see VFR conditions largely prevail this afternoon, as the aforementioned sea breeze pushes inland. As noted in the previous issuance, another round of nocturnal showers/storms could develop over the Atlantic and push onshore by early Thursday morning. Given that confidence in timing/location hasn't improved, have opted to continue with PROB30 groups at all TAF sites between roughly 08-12Z.

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

MARINE

Through Tonight: Southerly flow will continue through the evening, with winds averaging 15 kts or less. Otherwise, look for another round of nocturnal convection to be possible overnight into early Thursday, with seas generally ranging between 2 to 4 ft.

Thursday through Sunday: Atlantic high pressure will be the dominant synoptic feature through the weekend. This will generate a typical summertime wind field with increased winds along the land/sea interface each afternoon associated with the sea breeze. Marine conditions are expected to remain below Small Craft Advisory criteria through the weekend.

CHS WATCHES/WARNINGS/ADVISORIES

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