textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Hot and humid conditions continue into the weekend. A Heat Advisory is in effect today and Wednesday afternoon along the coastal corridor. Additional Heat Advisories will likely be needed, though an Extreme Heat Watch/Warning will also be possible, especially toward 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. Another round of strong to severe thunderstorms remain possible across portions of our area late Wednesday.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions continue into the weekend. A Heat Advisory is in effect today and Wednesday afternoon along the coastal corridor. Additional Heat Advisories will likely be needed, though an Extreme Heat Watch/Warning will also be possible, especially toward the end of the week.

Today: Latest surface observations indicate widespread heat indices of 105-110F with temperatures in the low to mid 90s and dew points in the mid to upper 70s. A Heat Advisory remains in effect for the coastal counties through 8 PM, but increasing coverage of showers and thunderstorms this afternoon could shorten the duration that heat indices stay at the 108 criteria, particularly along the southeast Georgia coast.

Wednesday: Similar to today, will see highs rise into the mid 90s, with dewpoints behind the sea breeze surging into the mid to upper 70s. This will yield heat index values up to 110 degrees east of I- 95. Thus, after collaboration with neighbors, have issued another Heat Advisory which will be valid 11 AM to 8 PM. We encourage folks to stay hydrated, take frequent breaks in the shade or AC, and check on vulnerable populations like children and the elderly.

Thursday and Friday: Upper level ridging amplifies during the later half of the week, which will result in the warmest temperatures of this heat wave. Highs in the upper 90s will be common, with perhaps a few locations briefly touching 100 degrees. These temperatures combined with dewpoints in the 70s will yield heat index values between 105-108 degrees west of I-95, with areas east soaring as high as 115 degrees. While additional Heat Advisories remain likely, can't rule out needing an Extreme Heat Watch/Warning for some locations.

This Weekend: Will see the aforementioned ridge shift a bit westward, resulting in a slight downtick of temperatures, especially Sunday with highs forecast in the low to mid 90s. Nonetheless, with dewpoints remaining in the 70s, will unfortunately see oppressive heat continue as heat index values reach upwards of 110 degrees along the coastal corridor.

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. Another round of strong to severe thunderstorms remain possible across portions of our area late Wednesday.

Rest of today: Radar imagery early this afternoon showed increasing coverage of showers and thunderstorms across the area. Focus for highest convective coverage through the remainder of the afternoon and early evening should be roughly Colleton county and south through southeast Georgia. Per SPC Mesoanalysis, the environment is characterized by 3000-3500 J/kg MLCAPE, steep low level lapse rates, and DCAPE on the order of 800-1000 J/kg. A few storms have the potential to become strong to severe, with damaging wind gusts being the primary hazard. In addition, locally heavy rainfall will be possible in any storm that develops. 12z HREF highlights coastal areas roughly Colleton county south to the Altamaha River as having the highest probabilities for 3-hr rainfall totals of >1 inch and even >3 inches. Localized flooding is possible. Convection should largely wane later this evening with loss of heating.

Wednesday: Upper level ridging continues to push eastward Wednesday, with the center becoming focused across the Gulf. As a result, NW to SE heights may align over our area. Latest guidance suggest that dry conditions should largely prevail through the afternoon, with precipitation chances then increasing through the evening and overnight period. Nonetheless, model consensus on timing and location still remain rather poor. While some CAMs support isolated storms mainly across southeast GA, others show an MCS tracking from upstate South Carolina into the Coastal Plains, suggesting that coverage could become a bit more widespread/displaced across our area. Given that there are a lot of factors in play that could cause this forecast to bust, want to emphasize that the severe threat will be highly conditional on how storms/boundaries evolve upstream. In the event that storms DO become severe, expect damaging gusts to be the primary hazard, along with brief heavy downpours and lightning.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Prevailing VFR through 18z Wednesday. Radar early this afternoon showed increasing coverage of showers and thunderstorms. There is potential for gusty winds and brief reductions in ceilings and visibilities within any storm that directly impacts the terminals, with highest probabilities of occurrence at KSAV. Coverage will wane overnight with loss of heating. Another round of showers and thunderstorms will be possible Wednesday, particularly at KSAV, however activity looks to occur beyond the valid TAF cycle.

Extended Aviation Outlook: Periodic flight restrictions may occur with any shower and thunderstorm late Wednesday. Otherwise, expect VFR conditions to prevail.

MARINE

The pressure pattern will support south winds around 10-15 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: A weak coastal trough will set up across the marine waters this week, persisting into the start of the weekend. Small Craft Advisories are not expected at this time, as southwesterly gusts remain around 15 to 20 kts, with seas between 2 to 3 ft.

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. For the evening high tide tonight (occurring at 749 PM in the Charleston Harbor), tide levels look to peak around 6.7-6.8 ft MLLW, with some probabilistic guidance indicating only a 10% chance of reaching 6.9 ft MLLW.

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