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 this afternoon and Sunday afternoon.

DISCUSSION

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

Today through Sunday: A warm pattern will remain in place with a large-scale ridge centered across the Deep South extending across the Southeast. Ample sunshine will promote strong sfc heating while a west-northwest downslope flow persists across the region. Guidance continues to support afternoon highs in the mid-upper 90s with a few locations potentially touching 100 degrees, which could result in record warmth (see Climate Section below). Humid conditions will also persist with sfc dewpts in the mid-upper 70s each day. Although the downslope flow should result in a slightly delayed seabreeze and some mixing out of sfc dewpts inland, moisture should pool near the boundary as it shifts inland as well as bring higher moisture content onshore. 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 108-115 range late morning into the afternoon and again on Sunday. Given today's setup, an Extreme Heat Warning is 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. Sunday should have similar results based on the persistent pattern. However, a slight uptick in convective coverage is possible with a front approaching nearby. Given some uncertainty in convection trends, have opted to remain heat headline free on Sunday. However, Heat Advisories will likely be needed over the area, and should convection hold of until late day, another Extreme Heat Warning could eventually be required along coastal counties Sunday afternoon.

Early to Middle of Next Week: Hot/humid conditions likely remain across the Southeast United States with the large-scale ridge extended across the region from the west-southwest. Record warmth is possible next week with latest guidance suggesting several areas of 100+ temps Monday/Tuesday and with little to no shower/thunderstorm activity. Conditions still remain hot heading through mid-week as well with humid conditions. Additional heat headlines are likely early into the middle of next week.

KEY MESSAGE 2: Strong to severe thunderstorms are possible this afternoon and Sunday afternoon.

The heat and humidity (mentioned in Key Message 1) will provide a moderate amount of instability across our area this afternoon and again Sunday afternoon. 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 both afternoons. 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 SATURDAY THROUGH WEDNESDAY/

VFR conditions are expected at CHS/JZI/SAV terminals through at least 18Z Saturday. The risk for isolated to scattered showers and/or thunderstorms increases during afternoon into early evening hours at all terminals. PROB30 groups for thunderstorms and MVFR conditions remain in place for CHS between 20-24Z today, JZI between 20-23Z today, and SAV between 21-23Z today, although latest guidance would suggest the CHS terminal having the best chance of direct impacts. A few thunderstorms could be strong with gusty winds. VFR conditions are then expected to prevail at all terminals between 00Z to 12Z Sunday.

Extended Aviation Outlook: Afternoon showers and thunderstorms will bring brief flight restrictions on Sunday.

MARINE

Tonight and Sunday: 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: KCHS: 101/1995 KCXM: 97/1995 KSAV: 100/1995

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

August 20: KCHS: 97/2005 KSAV: 102/1900

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

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

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

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for GAZ087-088-099>101-114-115-137. Extreme Heat Warning from 11 AM this morning to 8 PM EDT this evening for GAZ216>219-238>241. SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for SCZ040-042>044. Extreme Heat Warning from 11 AM this morning to 8 PM EDT this evening for SCZ045-147>152. MARINE...None.