textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Above normal temperatures will prevail across the region through the weekend and into next week. The next round of increased humidity and elevated heat indices will come this weekend into early next week, where Heat Advisories could be needed.

- 2) Summertime convection returns on Saturday, with chances persisting through the holiday weekend and into next week.

DISCUSSION

KEY MESSAGE 1: Above normal temperatures will prevail across the region through the weekend and into next week. The next round of increased humidity and elevated heat indices will come this weekend into early next week, where Heat Advisories could be needed.

Abnormally strong ridging aloft will remain the dominant synoptic feature across the region through the weekend and into early next week. At the surface, high pressure will extend into the region from the north today and Thursday, before a more typical subtropical high starts to take over this weekend. The position of the high for the rest of the day and through Thursday will drive northeasterly flow across the forecast area, which will bring seasonally below normal dewpoints in the low to mid 60s for majority of the area each day. Highs will still be in the low to mid 90s each day, but these low dewpoints will keep heat indices from outpacing air temperatures by much.

Ridging aloft begins to weaken into the weekend as the subtropical high takes hold over the weekend, with dewpoints rising back into the 70s. With temperatures similarly rising into the mid to upper 90s, heat indices this weekend and into next week could rise into the 105-100 degree range for some areas, especially for those along the coast. Therefore, the potential for Heat Advisories will increase over the weekend and into early next week. Record high temperatures and record high minimum temperatures will need to be monitored, see the climate section below where the forecast is near these records.

KEY MESSAGE 2: Summertime convection returns on Saturday, with chances persisting through the holiday weekend and into next week.

As the aforementioned ridge begins to weaken as it continues eastwards into the weekend, a weak surface trough will set up along/near the coast from North Carolina through South Carolina and into interior Georgia. Over the Atlantic, surface high pressure develops, with easterly winds aloft beginning to bring low-mid level moisture into the region on Saturday. Between the previously mentioned surface trough and the expected afternoon sea breeze, the return for daily scattered showers and thunderstorms is therefore expected, primarily in the afternoon hours with storm coverage waning into the evening. Latest guidance would suggest up to 20% chance for showers/storms Saturday afternoon, primarily across southeast Georgia, with higher moisture content arriving on Sunday as we switch to southwesterly flow aloft raising pops into the 20- 40% range.

Given the heat and humidity, daily instability values will be climbing into the 2-3 kJ/kg range, bringing chances for isolated strong to severe thunderstorms. However, with the lack of shear, organized convection is not expected with mostly cold-pool driven storms to monitor. Given PWATs as high as 1.5-2.0", locally heavy rainfall can also be expected.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR conditions will continue throughout the period, with wind direction changes being the main concern. Winds will remain breezy out of the east-southeast this afternoon, decreasing this evening and becoming calm overnight. Winds will be weak out of the northeast Thursday morning, becoming easterly by the afternoon.

Extended Aviation Outlook: Showers and thunderstorms may bring brief flight restrictions starting Saturday and persisting into the holiday weekend. Impacts are mostly likely each afternoon and evening.

MARINE

Northeasterly winds will weaken overnight as they become more easterly. Very weak low pressure off the Southeast Coast will yield winds from the NE or E through Thursday, with a surface high pressure slowly shifting toward the coast from the east-central CONUS. As the low further weakens and dissipates into Thursday night, winds will become southeasterly on Friday.

This weekend, surface high pressure will again build across the Atlantic region and become the dominant feature. This will swing winds around to become out of the southwest by early Saturday, becoming south-southeasterly throughout the afternoon. Expect similar conditions to unfold on Sunday, with winds expected to remain largely below small craft criteria, with highest chances for gusts into the mid 20s occurring behind the expected afternoon sea- breezes on Sunday.

Rip Currents: The combination of gusty onshore winds, along with a 2 ft swell at 9 to 10 seconds will generate a Moderate Risk of rip currents at our GA beaches for the rest of today.

CLIMATE

Record High Temperatures:

July 3: KCHS: 98/2019

July 4: KCHS: 98/2023 KSAV: 99/1997

July 6: KCHS: 100/1990

July 7: KCHS: 99/1954 KSAV: 101/1977

Record High Minimum Temperatures:

July 4: KCHS: 79/2016 KSAV: 79/1931

July 5: KCHS: 78/2017 KCXM: 82/2016 KSAV: 78/2016

July 6: KCHS: 79/1990 KCXM: 82/2024 KSAV: 78/2024

July 7: KCHS: 80/2017 KCXM: 82/2022 KSAV: 80/1883

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.