textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12z TAF issuance.

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, and Heat Advisories could be needed.

- 2) Summertime convection returns on Sunday, with chances increasing further 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, and 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 be the primary feature, first to the north on Thursday then taking on a more typical subtropical positioning as we move into the weekend and into early next week. The overall result of this setup will be above normal temperatures through the full forecast period. The hottest temperatures are expected over the weekend and into early next week, when widespread upper 90s are expected. For today, the setup will again favor below normal dewpoints with values falling into the mid to upper 60s for much of the area. Friday will feature another round of below normal dewpoints as well, but through the weekend and into early next week we will see the return of dewpoints well into the 70s, especially along the coast. This will yield heat index values only slightly higher than the air temperatures today and Friday. However, by Sunday and thereafter, the potential for heat indices into the 105-110 degree range will increase. Heat Advisories could be needed, especially from Sunday onward. Daily record high temperatures and record high minimums could be in play through the forecast period and that info is detailed in the Climate section below.

KEY MESSAGE 2: Summertime convection returns on Sunday, with chances increasing further into next week.

Strong ridging will be over the eastern half of the U.S. Friday morning. At the same time, there should be a broad, roughly 595 dam 500 mb High located to our north. This High should remain in place and gradually weaken late Friday into the 4th. Lower heights with potentially weak troughing will form over the Southeast U.S. Sunday and continue later into next week. Surface troughing will prevail across the Southeast U.S. Friday, continuing through the holiday weekend, and into next week. Meanwhile, High pressure will persist in the western Atlantic. This pattern will gradually usher more moisture into our region, with PWATs peaking ~1.5" on Friday, then gradually increasing closer to 2" on Sunday. The synoptic models and the NBM continue to keep Friday dry, which is reflected in the forecast. But they also trended drier on the 4th, which is bit of a change from the previous runs. We hesitantly followed this forecast route. But we also must stress that low POPs on the 4th don't mean zero convection. A stray shower or thunderstorm could briefly develop and bring some impacts. Regardless, the 4th is looking dry for a majority of our area.

Convection is more likely to return on Sunday. That's when afternoon POPs are limited to a slight chance POPs for our SC counties, our GA counties chance POPs. POPs are even higher for our entire area Monday onward, signaling more convective coverage and intensity. The most likely impacts will be each afternoon and evening. The convective setup will vary each day, depending on how much instability we get from the above normal high temperatures, the overall DCAPE values, and the inland movement of the sea breeze. However, due to low or minimal shear, organized convection is not expected, with mostly cold- pool driven storms. Regardless, strong to marginally severe thunderstorms are possible each day, with the main threat being damaging winds. Locally heavy rainfall can also be expected. Convection is then expected to dissipate each evening.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR conditions will prevail at KCHS, KJZI, and KSAV through 12z Friday.

Extended Aviation Outlook: Showers and thunderstorms may bring brief flight restrictions Sunday and Monday, with impacts most likely during the afternoon and evening.

MARINE

Today and tonight: Modest northeast flow mostly in the 10-15 knot range will prevail across the local waters through much of the day. Winds will turn more easterly and then southeasterly through the late afternoon and into the evening. Overnight, wind speeds will steadily diminish to be 5 knots or less. Seas will mostly average 2-3 feet, but potentially up to 4 feet at times in the outer GA waters.

Extended Marine: Surface troughing will prevail across the Southeast U.S. Friday, continuing through the holiday weekend, and into next week. Meanwhile, High pressure will persist in the western Atlantic. Onshore winds Friday afternoon, will clock around to the SE by Friday evening, followed by a turn to the SW early on the 4th. Winds will then have a typical summertime pattern for the holiday weekend into next week. 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, including across Charleston Harbor, as the sea breeze moves through later on the 4th, and 20-25 kt later Sunday and Monday. Each night, expect winds to veer. Seas should stay 4 ft or less. No Small Craft Advisories are expected.

Rip Currents: The combination of gusty onshore winds, along with a 2 ft swell at 8 or 9 seconds will generate a Moderate Risk of rip currents at our GA beaches 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 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.