textproduct: Charleston

WHAT HAS CHANGED

Key Message 1 was updated. The Aviation section was updated for the 00z TAFs.

KEY MESSAGES

- 1) Strong to severe thunderstorms are possible this afternoon and again Monday afternoon.

- 2)Increasing rain chances mid to late week with the potential for locally heavy rainfall.

DISCUSSION

KEY MESSAGE 1: Strong to severe thunderstorms are possible Monday afternoon.

The synoptic pattern aloft today and tomorrow will be similar, featuring large scale troughing along the eastern CONUS. A weak surface front will linger in the vicinity of the SC Midlands into the middle of the week. Shortwave troughs are expected to ripple across the southern periphery of the large scale troughing aloft today and Monday. This synoptic set up will allow for strong to severe thunderstorms to develop both this afternoon and again Monday afternoon.

Monday: Forecast soundings paint a similar picture to Sunday on Monday afternoon, however with PWATs increasing to around 1.7 to 1.8". Coverage of thunderstorms is forecast to be greater, with scattered to numerous PoPs in the forecast. DCAPE values are still forecast to be upwards of 1500 J/kg. Damaging wind gusts will again be the main hazard. Machine learning guidance shows the main threat area across SE Georgia, with slightly higher probabilities of damaging wind gusts than portrayed on Sunday. The current outlook from the Storm Prediction Center is another Marginal Risk (level 1 of 5).

KEY MESSAGE 2: Increasing rain chances mid to late week with the potential for locally heavy rainfall.

Wednesday through Thursday: The region will remain between a Bermuda high and low pressure over the Southern Plains. This pattern should support steady southwest H85 winds across the Deep South and Southeast U.S., aiding in rising PW values across the region. By Thursday, GFS forecast soundings indicate PW values exceeding 1.9" across SE GA and SC. As temperatures warm into the low to mid 90s, a sea breeze should develop each afternoon, pushing inland through the early evening hours. Instability could pool into moderate levels given dewpoints in the upper 70s to near 80 degrees. The forecast will indicate scattered to numerous PoPs for showers and thunderstorms.

Friday into Saturday: The GFS and ECMWF indicate that the weakness between the western Atlantic and south Rockies ridges will deepen across the region. A weak cold front could drape across the forecast area during the late week. In addition, an afternoon and evening sea breeze is expected to develop each day. Given warm and humid conditions across the region, the cold front and sea breeze boundaries should yield areas of numerous showers and thunderstorms.

This pattern may provide weak flow, resulting in storm motions around 15 mph. In addition, multi-cell storms could develop along the sea breeze and any outflow boundaries. Provided PW values near 2 inches, excessive rainfall could occur, especially over areas of recent heavy rainfall.

AVIATION /00Z MONDAY THROUGH FRIDAY/

24/00z TAFs: KCHS/KJZI/KSAV: VFR will prevail through much of the period through 25/00z. Risk for tstms will increase during the mid-late afternoon hours, especially near KSAV where confidence for some tstm impacts is the greatest. VCTS was introduced 21-00z for KSAV. Guidance suggests coverage may be more sparse around KCHS and KJZI, thus no mention of TSRA was included for this forecast cycle. The need for TSRA will be reevaluated for the 06z TAF cycle.

Extended Aviation Outlook: Scattered showers and thunderstorms are possible each afternoon potentially bringing temporary restrictions at the terminals.

MARINE

Through Friday: The pressure pattern should favor southwest winds between 10 to 15 kts. As a result, seas will likely remain between 2 to 3 ft. Any thunderstorms that move over the waters have the potential to bring higher wind gusts and frequent lightning, especially late Monday afternoon/evening off the GA and lower SC coast.

CLIMATE

Record High Minimum Temperatures:

August 24: KCHS: 76/2010 KCXM: 80/1975

August 25: KCHS: 77/1982

August 28: KCHS: 77/2020

CHS WATCHES/WARNINGS/ADVISORIES

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