textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12Z TAFs.

KEY MESSAGES

- 1) A Heat Advisory is in effect for the coastal counties this afternoon as hot and humid conditions make a return. Additional Heat Advisories will likely be required through the week and into the weekend. Extreme Heat Watches/Warnings cannot be ruled out, especially towards the end of the week.

- 2) Scattered to numerous thunderstorms will develop across southeast Georgia and the lower South Carolina Lowcountry, especially near the coast. A few storms may produce damaging wind gusts and heavy downpours this afternoon and evening. Additional severe thunderstorms are possible across portions of the region late Wednesday.

DISCUSSION

KEY MESSAGE 1: A Heat Advisory is in effect for the coastal counties this afternoon as hot and humid conditions make a return. Additional Heat Advisories will likely be required through the week and into the weekend. Extreme Heat Watches/Warnings cannot be ruled out, especially towards the end of the week.

Heat headlines are likely into the weekend as heat index values soar into the 100-110 range each afternoon through mid-week and upwards of 115 late in the week. The daily record highs and record high minimum temperatures will likely be challenged at our three climate sites (see Climate Section for more details). Given the very mild overnight periods and minimal coverage of precipitation, there will be few instances of relief from the heat this week and into the weekend.

Today and Wednesday: Ridging aloft will dominate over the southeastern states today and Wednesday, with high temperatures each day reaching into the mid 90s. Dew points will surge behind the sea breeze, likely reaching values in the mid to upper 70s. This will yield heat index values as high as 110 generally east of I-95. A Heat Advisory is in effect for the coastal counties today from 11 AM to 8 PM. Another Heat Advisory will likely be required for the same locations on Wednesday.

Thursday and Friday: The ridging aloft amplifies towards the end of the week, likely bringing the warmest temperatures of the heat wave. Highs on each day will likely reach into the upper 90s, with a brief moment of touching 100 not out of the question. Heat index values west of I-95 will likely reach 105-108 (Heat Advisory) with locations east of I-95 reaching heat index values as high as 115. Extreme Heat Watches/Warnings may be required for these locations.

This Weekend: The center of ridging aloft will shift slightly westward, resulting in a slight downtick of temperatures. However, heat index values are still forecast to reach upwards of 110 along the coastal corridor likely necessitating additional Heat Advisories.

KEY MESSAGE 2: Scattered to numerous thunderstorms will develop across southeast Georgia and the lower South Carolina Lowcountry, especially near the coast. A few storms may produce damaging wind gusts and heavy downpours this afternoon and evening. Additional severe thunderstorms are possible across portions of the region late Wednesday.

Tuesday: A sfc trough should remain across the central Carolinas into GA through this evening. Satellite water vapor shows an MCV over the middle AL/GA this morning, expected to ripple over SE GA this afternoon. In addition, the sfc trough to the west should draw the sea breeze inland this afternoon. Recent run of the HREF indicates that deep convection may begin to develop ahead of the MCV, likely forming several cool pools. Hot and humid conditions across the forecast area will likely yield SBCAPE values between 2500-3000 J/kg. In addition, forecast soundings indicate DCAPE values between 1000-1500 J/kg. Given the expansive field of DCAPE, the cool pools should travel long distances, potentially interacting with the sea breeze. This interaction should develop scattered to numerous thunderstorms along the coast, especially between Chatham and Charleston counties. The environment featuring moderate instability and DCAPE along with effective bulk shear around 20 kts may support a few severe thunderstorms, producing damaging wind gusts. The severe potential appears the greatest across Chatham, Jasper, Beaufort, and Colleton counties this afternoon. In fact, 0Z GEFS indicates that most of the forecast has a 5-15% neighborhood prob of damaging winds, with in excess of 15% near the mouth of the Savannah River. In addition to the severe risk, multicell storms may produce localize areas of heavy rainfall, with some locations receiving in excess of 3 inches. If a swath of heavy rain occurs over a coastal city, then Flash Flooding may occur.

Wednesday: The center of 595 DM ridge is forecast to slide west over the northern Gulf. As a result, NW to SE heights may align over the forecast area. NAM12 and CAMS indicate that at least isolated storms may develop over portions of SE GA Wednesday afternoon. Interestingly, the NAM12 and GFS shows an MCS tracking from the Upstate to the Coastal Plain Wed evening. Given the mid-level heights and lingering elevated instability, the potential for an MCS reaching the forecast appears high enough to increase PoPs Wednesday evening and overnight to at least SCHC. SPC has highlighted this potential severe weather with a Marginal Risk.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

12Z TAFs: The terminals will remain between a broad trough across the central Carolinas and Georgia and high pressure over the western Atlantic. This pattern will yield west-southwest winds across the terminals through the TAF period. The interaction of cold pools from the NW and a sea breeze should spawn scattered to numerous thunderstorms near KSAV, highlighted with a TEMPO from 20-24Z. Coverage of convection near KJZI and KCHS appears a bit less compared to KSAV, TAFs will highlight the primary thunderstorm time window with a PROB30 between 20-24Z.

Extended Aviation Outlook: Prevailing VFR.

MARINE

The pressure pattern will support south winds between 15 to 20 kts today, shifting from the southwest tonight. Wave heights are forecast to remain between 2 to 3 ft. Scattered to numerous thunderstorms may push over the nearshore waters late this afternoon and evening. A few of these storms may produce wind gusts in excess of 34 kts, especially the nearshore GA and lower SC waters.

Wednesday through Saturday: Conditions are expected to remain below Small Craft Advisory criteria this week and into the weekend. A weak coastal trough will set up across the marine waters this week, persisting into the start of the weekend. This set up will keep conditions across the marine waters breezy with southwesterly winds gusting around 15 to 20 knots. 2 to 3 ft seas are expected across the marine zones this week.

Coastal Flooding: While elevated tidal cycles are expected this week due to the upcoming perigee and new moon, the south- southwesterly surface flow should keep tidal departures low, limiting the overall coastal flood threat.

CLIMATE

Record High Temperatures:

August 11: KCHS: 98/1968 KCXM: 97/1954

August 12: KCHS: 98/1957 KCXM: 98/1998 KSAV: 100/1999

August 13: KCHS: 100/1995 KCXM: 98/1913 KSAV: 98/2010

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

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

Record High Minimum Temperatures:

August 10: KCHS: 80/2007 KSAV: 79/2024

August 11: KCHS: 79/1983 KCXM: 82/2021 KSAV: 78/1878

August 12: KCHS: 79/1999 KSAV: 80/1878

August 13: KCHS: 81/2023 KCXM: 83/2023 KSAV: 81/2023

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 KSAV: 78/2019

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for GAZ217>219-239>241. SC...Heat Advisory from 11 AM this morning to 8 PM EDT this evening for SCZ148>152. MARINE...None.