textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Heat will remain a concern into late week.

- 2) Afternoon and evening thunderstorm coverage will remain isolated through Thursday. An increase in thunderstorm coverage is expected Friday through the weekend.

DISCUSSION

KEY MESSAGE 1: Heat will remain a concern into late week.

Coastal troughing at the surface with ridging aloft will continue the heat wave into the end of the week. Temperatures are in the mid- upper 90s this afternoon, with a few more degrees likely before peak heating ends. Areas along/west of the I-95 corridor will continue to see a westerly component to the winds this afternoon, which will advect and mix in some drier air into the environment. This will result in dew points dropping down into the upper 60s to lower 70s, keeping heat index values in the 100-107 degree range this afternoon. Areas along the coast will see a sea-breeze push ashore this afternoon, keeping dewpoints in the mid to upper 70s which will result in heat index values of 108-112 deg F this afternoon. While we may end up on the upper end of guidance today, the previously issued Heat Advisory looks to be in good shape. Daily highs and daily high minimums are both possible today, for more see the climate section below.

Rinse and repeat for Thursday and Friday. Given the continuation of similar conditions, have issued another Heat Advisory for the coastal corridor and inland Berkeley county Thursday from 11 AM to 8 PM, where heat index values will peak from 108 to 112 deg F. Friday looks be a touch cooler given slightly earlier shower/thunderstorm initiation and more areal coverage, but will likely see similar coverage of heat prior to showers/storms starting.

An increase in shower and thunderstorm activity this weekend looks to cool us off enough to possibly go without any heat advisories/warnings, though high temperatures look to still peak in the lower to mid 90s.

KEY MESSAGE 2: Afternoon and evening thunderstorm coverage will remain isolated through Thursday. An increase in thunderstorm coverage is expected Friday through the weekend.

Coastal troughing at the surface and ridging aloft will allow for isolated chances for showers and thunderstorms during the afternoon and evening hours today and Thursday. Showers/storms will likely initiate off of either the coastal trough or the expected sea- breeze, but as neither will be particularly fast moving, only a few isolated showers and storms are expected. Models continue to suggest portions of southeast South Carolina are the primary region where rainfall is possible, with probabilities in the 20-40% chance range. Similar to the past couple days, while the environment has 2000-2500 J/kg of CAPE resulting in the possibility of an isolated strong- severe thunderstorm, the lack of forcing and the lack of shear and upper level flow has kept such activity from occurring which should continue today. Expect a similar repeat of shower and thunderstorm chances for Thursday.

Friday and into the weekend, a slow moving trough begins to move across the region, increasing rainfall chances into the weekend. With temperatures remaining near/above normal, SBCAPE and DCAPE values could still get quite elevated. Strong to severe thunderstorms remain possible each afternoon with the main threat being damaging winds. Heavy rainfall will also be concern due to the very weak steering winds and elevated PWATs.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

18Z TAFs - Generally VFR conditions expected, though the risk for isolated showers and thunderstorms builds this afternoon, with greatest chances (~20-40%) for portions of southeast South Carolina. Storms will likely hold off on initiating until the sea breeze pushes north-northwest of JZI, but did include a PROB30 for CHS as chances increase inland. SAV looks to remain clear of shower/storm activity. In addition to potentially producing MVFR conditions, a few thunderstorms could be strong with gusty winds. Rain chances decrease overnight. Areas that see decent amounts of rain may see patchy fog into Thursday morning, but did not include any mention at the TAF sites. After a quiet morning, chances for isolated showers/storms return Thursday afternoon.

Extended Aviation Outlook: Isolated afternoon flight restrictions are possible in showers and thunderstorms on Thursday. Shower and thunderstorm chances increase Friday into the weekend, bringing additional chances for brief flight restrictions.

MARINE

There are no large-scale marine concerns. Mornings will generally start out with south-southwesterly winds, increasing in strength as they become southeasterly in the afternoon, and back to south- southwesterly overnight. Seas mostly in the 2-3 ft range. There may be some isolated showers/storms that move out into the waters today and Thursday afternoon, with coverage increasing Friday into the weekend.

CLIMATE

Record High Temperatures:

August 19: KCHS: 98/1983 KCXM: 98/1895 KSAV: 99/1900

August 20: KCHS: 97/2005 KCXM: 99/1902 KSAV: 102/1900

August 21: KCHS: 100/1983 KCXM: 99/1900 KSAV: 101/1902

Record High Minimum Temperatures:

August 19: KCHS: 79/2010 KCXM: 83/2021 KSAV: 79/1878

August 20: KCHS: 78/2017 KCXM: 82/2017 KSAV: 82/1878

August 21: KCHS: 79/2010 KCXM: 82/2023 KSAV: 80/1902

August 22: KCHS: 79/2023 KCXM: 82/2014 KSAV: 79/1902

August 23: KCHS: 80/2014 KCXM: 81/2019 KSAV: 78/2016

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory until 8 PM EDT this evening for GAZ217>219- 239>241. Heat Advisory from 11 AM to 8 PM EDT Thursday for GAZ217>219- 239>241. SC...Heat Advisory until 8 PM EDT this evening for SCZ045-148>152. Heat Advisory from 11 AM to 8 PM EDT Thursday for SCZ045- 148>152. MARINE...None.