textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Increased chances for showers and thunderstorms early this week, with an isolated strong/severe storm possible across the interior this afternoon into early evening.

DISCUSSION

KEY MESSAGE 1: Increased chances for showers and thunderstorms early this week, with an isolated strong/severe storm possible across the interior this afternoon into early evening.

Aloft, a similar setup remains across the region today along the western periphery of an Atlantic ridge, with h5 shortwave energy rippling across the Deep South and Southeast United States and promoting shower and thunderstorm development across a moist (PWAT 1.8 to 2.0 inches) and warm environment this afternoon into early evening. Convection today should occur in two waves. The first is ongoing with numerous shower and thunderstorms developing near and inland of a sea breeze circulation across Southeast South Carolina. This convection is likely to remain sub-severe given an earlier start today and a lack of stronger deep-layer shear, but still capable of producing gusty winds up to 35-45 mph and heavy downpours during early-mid afternoon hours with a focus of heaviest rainfall across a stretch from Dorchester into Berkeley Counties going forward. Hourly rainfall rates exceeding 2 inches per hour could lead to minor flooding, especially in poorly drained areas.

The second wave of convection should arrive across Southeast Georgia late afternoon, in a slightly more unstable environment marked by MLCAPE around 2000-2500 J/kg, but still within weaker shear (0-6 Bulk Shear around 20 kt). Some hires guidance seems to be picking up on this scenario, with convection spreading across Southeast Georgia mid-late afternoon when sfc high temps have peaked in the upper 80s and where mid 70 dewpts reside along/ahead of a sea breeze circulation making way inland. Additionally, an outflow boundary has developed from ongoing convection across Southeast South Carolina and has entered Southeast Georgia early this afternoon, which could provide another focus for convection to initiate and/or become enhanced during peak heating hours across or just inland to the local area. Similar to the previous day, the environment should support numerous to widespread showers and thunderstorms spreading into the area from the south/southwest by late afternoon hours, with a few storms embedded in convective clusters capable of producing damaging wind gusts given favorable low-lvl lapse rates (7 C/km) and DCAPE (700-900 J/kg) during peak heating. Activity should wane by mid evening hours as instability weakens due to the loss of daytime heating. The Storm Prediction Center continues to highlight much of Southeast Georgia in a Marginal Risk for severe weather along/west the I-95 corridor in the Day 1 Convective Outlook.

Another concern with late day/early evening convection is localized heavy rainfall, given corfidi vectors indicating slow storm motions generally around 10 kt or less in a highly moist environment (PWATs 1.8-2.0 inches) and activity running parallel to the inland approaching sea breeze. Similar to yesterday, WPC has highlighted inland tier counties across Southeast Georgia and Southeast South Carolina (west of I-95) in a Day 1 Excessive Rainfall Outlook.

Memorial Day: Conditions are not expected to change much from today, with comparable temperatures and moisture content. The sea breeze will again be the focus for the initial thunderstorm activity, then coverage should expand across inland areas. Locally heavy rainfall is possible generally along and west of I-95.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

TEMPO MVFR conditions have been included at CHS/JZI/SAV for afternoon showers/thunderstorms likely to impact the terminals between 18-20Z. Thereafter, VFR conditions should prevail late afternoon through overnight hours. However, additional flight restrictions are possible should showers/thunderstorms redevelop late day, particularly at SAV. There are some hints of potential MVFR cigs at the SAV terminal late tonight, but confidence remains too low to include in the latest TAF issuance. PROB30 groups have been introduced at all terminals between 16-18Z Monday for isolated thunderstorms developing along a sea breeze.

Extended Aviation Outlook: TEMPO flight restrictions possible with showers and thunderstorms at CHS/JZI/SAV terminals during the afternoon hours through the week.

MARINE

This Afternoon and Tonight: High pressure centered over the western Atlantic will remain the dominant feature across local waters, favoring south-southeasterly winds generally around 15 kt today (slightly higher along the land/sea interface), then topping out in the 15-20 kt range overnight. Seas will range between 3-5 ft, largest across outer waters overnight.

Monday through Friday: Conditions are forecast to remain below Small Craft Advisory criteria through the week, with daily chances for showers and thunderstorms. High pressure to the east will drive onshore ESE flow each day, with wind speeds mostly topping out in the 10-15 knot range. Each afternoon and evening there could be some local enhancement along the land/sea interface with the diurnal sea breeze. Seas will average 2-4 feet through the period.

Rip Currents: A modest easterly swell around 3-4 ft/8s and sea breeze influences each afternoon will keep the rip current risk in the moderate category at all area beaches through at least Tuesday.

CHS WATCHES/WARNINGS/ADVISORIES

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