textproduct: Charleston

WHAT HAS CHANGED

All of the sections were updated.

KEY MESSAGES

- 1) Scattered to numerous showers and thunderstorms will impact the region into this evening. Locally heavy rainfall is possible along with a risk for an isolated strong to severe thunderstorm.

- 2) A typical summertime pattern returns through the weekend, with isolated strong to severe thunderstorms possible each day.

DISCUSSION

KEY MESSAGE 1: Scattered to numerous showers and thunderstorms will impact the region into this evening. Locally heavy rainfall is possible along with a risk for an isolated strong to severe thunderstorm.

The mid-levels consist of a cut-off Low over the Southeast U.S. It'll gradually shift north into the overnight. At the surface, a stationary front is located to our west and northwest, and it's expected to dissipate around daybreak Wednesday. PWATs across our area are lower compared to the past few days. Though, they remain around 2", depending on the time period and location. Temperatures in the upper 80s to lower 90s are generating decent instability. SPC Mesoscale Analysis shows MLCAPEs in the 1,500-2,000 J/kg range, with DCAPEs around 1,000 J/kg in some locations. Effective bulk shear is 25-30 kt. This has generated convection across portions of our inland locations this afternoon. CAMs generally have it increasing in coverage and intensity along and west of the I-95 corridor late this afternoon into this evening, aided partly by the sea breeze. There is a risk for an isolated strong to severe thunderstorm through early this evening, with damaging winds being the primary threat. Locally heavy rainfall is also possible into this evening. Convection should then shift mostly offshore late this evening and overnight, with a band remaining pointed towards Charleston County and vicinity.

KEY MESSAGE 2: A typical summertime pattern returns through the weekend, with isolated strong to severe thunderstorms possible each day.

As the Atlantic ridge strengthens offshore of the Eastern Seaboard, yielding south-southwesterly flow across the Southeast. This persistent plume of moisture will maintain PWAT values ~2 inches, with the highest moisture generally located along and east of the I- 95 corridor. This pattern will support a typical summertime pattern with the afternoon sea breeze and remnant outflow boundaries serving as the main focus for afternoon/evening convection.

High PWAT values combined with deep warm-cloud layers will support very efficient rainfall production, with rates of 1-2 inches per hour possible beneath the strongest thunderstorms. Additionally, these showers and thunderstorms will be moving on the slower side (storm motions of ~10kt), meaning localized flooding will likely be the main threat for each afternoon/evening (esp. in low-lying and/or poor drainage areas). While instability remains quite limited on Wednesday, pockets of 1500-2000 J/kg of SBCAPE still appear possible where sufficient heating occurs. And then, Thursday through Saturday, instability will be able to build a bit more in the afternoons/evenings than Wednesday yielding a better chance for a severe risk. Also, forecast soundings indicate DCAPE values of 800- 1000 J/kg each afternoon/evening as well, which could support a few storms capable of producing damaging wind gusts. Thus, an isolated severe thunderstorm cannot be ruled out completely for each afternoon/evening as damaging wind gusts and cloud-to-ground lightning could be possible within a stronger cell.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

18Z TAFs: Radar indicates convection inland this afternoon. The CAMS have the convection increasing in both coverage and intensity over the next few hours. Various impacts are expected at each TAF site, ranging from VCSH, to TEMPO MVFR due to TSRA. Amendments may be needed to the TAFs based on future radar trends. Convection is expected to persist near KCHS and KJZI overnight into Wednesday. Though, KSAV should dry out late this evening and remain that way into Wednesday.

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

MARINE

Through Tonight: S winds around 15 kt this evening will transition to the SSW overnight, easing to 10-15 kt by daybreak Wednesday. Seas should be in the 3-4 ft range.

Wednesday through Saturday: As high pressure situates itself across the Atlantic, a typical summertime pattern will take shape for the local waters through the period. Expect increased winds along the land/sea interface as the afternoon seabreeze kicks inland each day. East-southeasterly swell will continue through the weekend with seas ranging from 2 to 4 ft.

Rip Currents: There is a Moderate risk of rip currents for the Charleston County beaches through this evening.

CHS WATCHES/WARNINGS/ADVISORIES

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