textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated

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.

A rather long duration heat wave has taken hold across the area and relief from the heat does not look to come until later next week. Large-scale ridging centered across the Deep South extending into the coastal Southeast will remain in place through the foreseeable future leading to continued heat issues through at least Wednesday possibly Thursday of next week. Ample sunshine will promote strong sfc heating each day 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 mainly on Monday and Tuesday of this week, 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.

Rest of today through Sunday: So far observations across the area are on track with widespread 108 to 113 heat indices across the area. The highest heat indices look to be along the immediate coastline as the seabreeze has begun its slow march inland. Scattered storms have begun to develop this afternoon north of the area across northern SC and this activity is expected to slowly build southward into our area likely bringing temporary relief tonight for some locations. Further south relief may not come; however, confidence across Georgia in higher heat indices is lower thus things should even out across the board tonight. Sunday should have similar results based on the persistent pattern. However, a slight uptick in convective coverage is possible as a subtle shortwave moves across the area and a weak boundary encroaches from the north. Storms may also begin earlier in the day closer to the noon timeframe which will help "limit" how hot we get during the afternoon. Given some uncertainty in convection trends, have opted to go with a Heat Advisories over the area.

Early to Middle of Next Week: The resurgence in the hot/humid conditions looks likely on Monday and Tuesday as the upper ridge restrengthens across the area. Record warmth looks possible with latest guidance suggesting several areas of 100+ temps Monday/Tuesday and with little to no shower/thunderstorm activity. Heat indices will likely climb into the 110 to 115 range almost area wide and some isolated coastal areas may approach heat indices of near 120. Conditions still remain hot heading through mid-week as the upper ridge slowly backs off heading into the weekend. 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 /18Z SATURDAY THROUGH THURSDAY/

18Z TAFs - The risk for isolated to scattered showers and thunderstorms builds this afternon, with chances for those in the Dorchester/Charleston/Berkeley county region, and also in southeastern Georgia primarily along the Altamaha River Valley. For CHS and JZI, did upgrade to TEMPO groups while delaying them to be 1522-1602Z, while keeping a PROB30 group for SAV. In addition to potentially producing MVFR conditions, 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: Periodic flight restrictions are expected in showers and thunderstorms through next week.

MARINE

Through Sunday: Surface high pressure over the western Atlantic with weak inland troughing will continue the mostly quiet conditions over the waters. Expect westerly to southerly winds throughout the period, with the breeziest winds occurring both afternoons along the land-sea interface with gusts to 20 knots. Thunderstorms that develop over land this afternoon and Sunday afternoon could shift offshore during the later afternoon into early evening hours. A few thunderstorms could remain strong when shifting across coastal areas.

Monday - Wednesday: 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 until 8 PM EDT this evening for GAZ087-088- 099>101-114-115-137. Heat Advisory from 11 AM to 8 PM EDT Sunday for GAZ087-088- 099>101-114-115-137-216>219-238>241. Extreme Heat Warning until 8 PM EDT this evening for GAZ216>219-238>241. SC...Heat Advisory until 8 PM EDT this evening for SCZ040-042>044. Heat Advisory from 11 AM to 8 PM EDT Sunday for SCZ040-042>045- 147>152. Extreme Heat Warning until 8 PM EDT this evening for SCZ045- 147>152. MARINE...None.