textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated for the 12Z TAF issuance.

KEY MESSAGES

- 1) Heat will remain a concern into the middle of next week.

- 2) Strong to severe thunderstorms are possible each afternoon through the weekend.

DISCUSSION

KEY MESSAGE 1: Heat will remain a concern into the middle of next week.

Today and Saturday: A warm pattern will remain in place with a large- scale ridge across much of the Deep South and Southeast United States through the weekend. Ample sunshine will promote strong sfc heating in advance of afternoon convection each day, with 1000-850mb thickness values supportive of afternoon highs in the mid-upper 90s, with a few locations potentially touching 100 degrees away from the coast, which could result in some record warmth (see Climate Section below). In addition to hot temperatures, conditions will remain humid with sfc dewpts in the mid-upper 70s each day. A west-northwest downsloping wind should result in a slightly delayed seabreeze the next few afternoons, promoting some mixing out of sfc dewpts inland, but moisture pooling along/near the sea breeze will eventually shift higher moisture content onshore each day for at least a few hours as well. This will likely result in the higher heat/moisture combination along coastal zones (along/east of I-95) for the next couple days, with heat index values up to the 110-115 range late morning into the afternoon and again on Saturday. Given the setup and expected heat index values, an Extreme Heat Warning remains in effect for coastal counties from 11 AM to 8 PM today while remaining areas are included in a Heat Advisory for the same time period. The slightly more favorable position of the synoptic ridge supports slightly higher heat index values along the coastal corridor Saturday, especially if convection holds off longer than anticipated mid-late afternoon. Therefore, an Extreme Heat Watch has been issued for all Southeast SC/GA coastal zones from 11 AM to 8 PM Saturday. Another Heat Advisory could be needed for inland areas on Saturday as well.

Early to Middle of Next Week: Hot/humid conditions likely remain across the Southeast United States late weekend into the middle of next week with the large-scale ridge centered over or nearby, although a front could lead to greater shower/thunderstorm coverage that limits maximum heat conditions Sunday. Record warmth is possible next week with guidance suggesting several areas of 100+ temps Monday/Tuesday and little to no shower/thunderstorm activity. Additional heat headlines are likely early into the middle of next week.

KEY MESSAGE 2: Strong to severe thunderstorms are possible each afternoon through the weekend.

The heat and humidity (mentioned in Key Message 1) will provide a moderate amount of instability across our area each afternoon through the weekend. Depending on the model, SBCAPE values peak in the 2,000-2,500 J/kg range, with DCAPE values upwards of 800 J/kg. There are some minor differences amongst the various near-term CAMS and even the synoptic models. But the general consensus is that there should be isolated to scattered convection each afternoon through the weekend. These details will need to be refined with each forecast. But the storms are most likely to start along the sea breeze and then shift inland, with outflow and boundary interactions playing a role in storm formation and persistence. Given the aforementioned instability, strong to severe thunderstorms are possible. The main threat would be damaging winds. But heavy rainfall is also a concern due to weak steering flow. Backbuilding and/or training of storms could drop enough rainfall to generate very localized flooding. The convection each afternoon is expected to dissipate each evening.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

VFR conditions are expected at CHS/JZI/SAV terminals through at least 18-19Z Friday. The risk for isolated to perhaps scattered showers and/or thunderstorms increases this afternoon into early evening hours. PROB30 groups for thunderstorms and MVFR conditions remain in place at CHS/JZI between 20-23Z Friday and at SAV between 21-24Z Friday. Gusty winds could also accompany thunderstorms. VFR conditions are then expected to prevail at all terminals between 00-12Z Saturday.

Extended Aviation Outlook: Afternoon showers and thunderstorms will bring brief flight restrictions through the weekend.

MARINE

Today and Tonight: Conditions are expected to remain quiet across local waters between the western periphery of an Atlantic high and weak troughing inland, although thunderstorms that develop over land could shift offshore late afternoon into early evening hours. A few thunderstorms could remain strong when shifting across coastal areas. Outside thunderstorms, southwesterly winds around 10 kt this morning should turn more southerly and gust up to 15-20 kt this afternoon, then persist into evening hours, before slowly weakening and returning to a southwesterly direction overnight. Seas should be no larger than 2-3 ft.

Extended Marine: There will be areas of High pressure in the western Atlantic and the northern Gulf, while surface troughing will be over the Southeast U.S. The interaction between all of these synoptic features will generate a typical summertime wind pattern. Winds will generally be from the SW, backing a bit each day and veering some each night. The strongest winds should be during the day, especially closer to the coast due to the sea breeze. Seas will mainly be in the 2-3 ft range.

CLIMATE

Record High Temperatures:

August 14: KCHS: 102/1995 KSAV: 102/1925

August 15: KCHS: 96/2023 KCXM: 99/1918 KSAV: 100/1918

August 16: KCHS: 99/1954 KSAV: 100/1954

August 17: KCHS: 102/1954 KSAV: 102/1954

August 18: KCXM: 97/1995 KSAV: 100/1995

Record High Minimum Temperatures:

August 14: KCHS: 80/2023 KCXM: 83/2023 KSAV: 80/2023

August 15: KCHS: 78/1995 KCXM: 83/2021 KSAV: 80/1995

August 16: KCHS: 78/2019 KCXM: 83/2016 KSAV: 78/2019

August 17: KCHS: 80/2017 KCXM: 83/2017 KSAV: 78/2017

August 18: KCHS: 80/2017 KCXM: 82/2017 KSAV: 78/2010

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory until 8 PM EDT this evening for GAZ087-088- 099>101-114-115-137. Extreme Heat Warning until 8 PM EDT this evening for GAZ216>219-238>241. Extreme Heat Watch from Saturday morning through Saturday evening for GAZ216>219-238>241. SC...Heat Advisory until 8 PM EDT this evening for SCZ040-042>044. Extreme Heat Warning until 8 PM EDT this evening for SCZ045- 147>152. Extreme Heat Watch from Saturday morning through Saturday evening for SCZ045-147>152. MARINE...None.