textproduct: Charleston

WHAT HAS CHANGED

All section have been updated.

KEY MESSAGES

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

- 2) Summertime convection returns on Friday and is expected to persist through the holiday weekend and into next week.

DISCUSSION

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

Aloft, prominent ridging will remain the primary feature influencing the region through the rest of the week and the upcoming weekend. This will support an environment of above normal temperatures and widespread low to mid 90s through the week. However, heat indices will likely be held down by below normal dewpoints, especially Wednesday and Thursday. By the weekend, the subtropical high at the surface will become more deeply rooted which will drive a more common southwesterly surface flow. This will yield dewpoints back into the 70s over the weekend, coincident with high temperatures in the mid to upper 90s. The end result will be elevated heat indices over the weekend and into early next week along with a rising probability of needing Heat Advisories for at least portions of the forecast area.

KEY MESSAGE 2: Summertime convection returns on Friday and is expected to persist through the holiday weekend and into next week.

Strong ridging will be over the eastern half of the U.S. Friday morning, with a roughly 595 dam 500 mb High located to our north. This High should remain in place and gradually weaken late Friday through the holiday weekend. Surface troughing will strengthen over the Southeast U.S. Friday and persist through the holiday weekend, while High pressure is in the western Atlantic. This pattern will gradually usher more moisture into our region. The combination of the weakening ridge, additional moisture, along with instability from above normal high temperatures will cause summertime convection to return on Friday, and gradually increase through the holiday weekend. The convective setup will vary somewhat each day, primarily due to the mesoscale setup, and forcing from the sea breeze. But the most likely times for convection will be each afternoon and evening. Any storms will have the potential to be strong to borderline severe, with the greatest threat being damaging winds, along with having locally heavy rainfall.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

The 12z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. Overall, VFR conditions are expected to prevail at all 3 sites through the entire TAF period though we will have to watch for shower and thunderstorm development near KSAV this afternoon. To account for this we have included a PROB30 group from 19-22z. Otherwise, the forecast is mainly dealing with wind direction changes from northeast flow in the morning to east- southeast in the afternoon with the passage of the sea breeze.

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

MARINE

Today and tonight: The local waters will be situated between an area of low pressure to the east and high pressure inland. This setup will drive northeast flow across the waters with enough of a pinched gradient to support 15-20 knots of flow, and even a few gusts up to 25 knots across portions of the SC nearshore waters this afternoon and into the early evening. Winds will be a bit more out of the east- northeast overnight, with speeds around 15 knots. Seas will tick upward a bit, and average 2-4 feet for most of the period.

Extended Marine: Very weak Low pressure off the Southeast Coast will yield winds from the NE or E through Thursday. As the Low dissipates Thursday night, winds will become light and variable. Then, they will clock around to the SE by Friday afternoon, followed by the SW early on the 4th. Winds will then have a typical summertime pattern for the holiday weekend. This will consist of some backing during the day, with the highest winds along the land/sea interface with the formation of the sea breeze. Gusts could approach 20 kt, especially in Charleston Harbor as the sea breeze moves through. At night, expect winds to veer. Seas should stay 5 ft or less. No Small Craft Advisories are expected.

Rip Currents: The combination of gusty NE winds and a 2 ft swell at 9 or 10 seconds will generate a Moderate Risk of rip currents at all of our beaches today, and a Moderate Risk at our GA beaches on Wednesday.

CLIMATE

Record High Temperatures:

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

Record High Minimum Temperatures:

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

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

CHS WATCHES/WARNINGS/ADVISORIES

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