textproduct: Charleston

WHAT HAS CHANGED

Key Message 1 has been updated for precipitation trends this evening. The Aviation Section has been updated for the 00Z Thursday TAF issuance.

KEY MESSAGES

- 1) Periodic showers and thunderstorms are expected to continue through the weekend.

DISCUSSION

KEY MESSAGE 1: Periodic showers and thunderstorms are expected to continue through the weekend.

Through Tonight: Latest radar trends indicate shower and/or thunderstorm coverage diminishing significantly with diurnal heat loss and a lack of significant forcing in place. Although a stray shower is possible during evening hours, the bulk of the area is expected to remain dry for the remainder of the evening and overnight.

Thursday and Thursday night: This time period is likely the most interesting due to the expected close passage of the remnant circulation of Arthur during the evening and overnight. Model consensus suggests that the morning and the first part of the afternoon should be relatively quiet. Thunderstorm activity is expected then increase from the west late in the afternoon and through the evening as the remnant circulation shifts through central GA and into the SC Upstate and Midlands. Though the best forcing and greatest coverage is expected to be focused to the northwest and north, the forecast will sit solidly on the periphery of a threat of severe weather and heavy rainfall. Model soundings show the potential for 30-40 knots of deep layer shear and possibly some backing of the low-level flow depending on the condition of the remnant circulation. Instability will be weak, but any thunderstorms that develop in the evening through early morning hours will need to be watched closely for a damaging wind threat. The potential for locally heavy rainfall will come mainly from training storms thanks to a relatively fast storm motion. Shower and thunderstorm potential should begin to wane as sunrise Friday approaches and the circulation starts to pass to the east.

Also of note for Thursday will be a return of temperatures into the low 90s. With dewpoints getting into the mid to upper 70s along the coastal corridor, we will likely see heat index values up to around 105 with pockets potentially up to 107-108.

Friday through Sunday: Another active day appears likely Friday as the forecast area sits ahead of a cold front approaching from the north. Mid-level flow will continue to be elevated, yielding some available shear in the presence of a warm moist and unstable environment. A few severe storms with damaging wind gusts will be possible. The front should sag through the area by Saturday and we expect to see a return to a more typical summertime pattern of diurnal showers and thunderstorms for the weekend.

AVIATION /00Z THURSDAY THROUGH MONDAY/

VFR conditions should prevail at CHS/JZI/SAV terminals tonight through at least 15Z Thursday. Chances for showers and thunderstorms increase at all terminals during afternoon hours Thursday, with highest confidence occurring at SAV by around 18Z, then at CHS/JZI starting around 20Z. Have introduced VCSH at SAV to account for precip activity from 18-24Z Thursday along with a PROB30 group for thunderstorms and MVFR conditions. PROB30 groups for thunderstorms with MVFR conditions have also been added from 20-24Z at CHS/JZI. Outside shower/thunderstorm activity, southwesterly winds are expected to become breezy at all terminals by around 14-15Z Thursday with peak gusts generally in the 20-25 kt range early and mid afternoon.

Extended Aviation Outlook: VFR conditions should largely prevail through the weekend, with brief periods of flight restrictions possible with any showers and thunderstorms.

MARINE

Tonight through Friday: Gusty southwest winds are expected across the waters through late week in between high pressure offshore and an approaching cold front and remnants of Arthur. While a few gusts around 25 knots are possible through tonight, especially over the SC waters, the time period of most concern is Thursday night into Friday when gusts reach 25-30 kts and seas build to 4-6 feet. Small Craft Advisories have been issued for all coastal waters outside of the Charleston Harbor (though one will likely be needed here at some point as well). A few gusts in the low 30 kt range are possible, but should largely stay shy of gale force. NBM probs for gusts >34 knots is generally 30-40%.

Saturday through Monday: Marine conditions will subside Saturday with no additional concerns through the weekend. Another front could approach the area on Monday, potentially leading to increasing winds and seas.

Rip Currents: Increasing swells and gusty winds will lead to an elevated risk of rip currents on Friday. Local rip current calculations produce a Moderate Risk at Charleston county beaches, with a Low elsewhere.

CLIMATE

Record High Minimum Temperatures:

June 18: KCHS: 78/2015 KCXM: 81/1998

June 19: KCHS: 79/2025 KCXM: 81/2025 KSAV: 79/1881

June 22: KCHS: 79/2018 KSAV: 78/1937

June 23: KCHS: 78/2024 KCXM: 82/1998 KSAV: 77/2017

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory from 2 PM Thursday to 8 PM EDT Friday for AMZ360. Small Craft Advisory from 8 PM Thursday to 8 PM EDT Friday for AMZ362. Small Craft Advisory from 2 AM to 5 PM EDT Friday for AMZ364. Small Craft Advisory from 2 AM to 8 PM EDT Friday for AMZ384.