textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Above normal temperatures expected to impact the area during the next 7 days with humidity levels increasing late weekend into next week. Heat Advisories possible starting Sunday, then each afternoon through much of next week.

- 2) Typical summertime convection returns on Sunday, with chances increasing further into next week.

DISCUSSION

KEY MESSAGE 1: Above normal temperatures expected to impact the area during the next 7 days with humidity levels increasing late weekend into next week. Heat Advisories possible starting Sunday, then each afternoon through much of next week.

A strong ridge will hold across the region this weekend and throughout much of next week, setting the stage for above normal high temperatures in the mid-upper 90s each afternoon and possibly a few spots that touch 100 degrees. Sfc dewpts will remain relatively low today and Saturday, dipping into the mid 60s across inland areas during peak heating hours. The combination of heat and moisture supports heat index values around 100 degrees today, then in the 100- 105 degree range on Saturday as moisture levels steadily increase and a south/southeasterly wind shifts a marine layer onshore. Sunday still looks like the first day where a larger area of heat index values in the 108-110 range are possible, with the greatest risk for Heat Advisory criteria being met along the coastal corridor where sfc dewpts remain the mid-upper 70s during peak heating hours. Expect similar conditions with the mid-upper lvl ridging holding across the Southeast and an afternoon onshore flow in place along the western periphery of the Atlantic sfc high. Heat Advisories could be needed each afternoon for much of the week, especially along the coastal corridor. However, slightly higher shower and thunderstorm coverage associated with a nearby approaching front could limit heat index values mid-week. Outside of this possibility, daily record high temperatures and record high minimums could be challenged at times throughout the week. See the Climate Section below for details.

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

As this strong upper-lvl ridge slowly breaks down over the holiday weekend, weak troughing will develop across the Eastern seaboard as a shortwave skirts across the U.S./Canadian border. This pattern will allow for moisture to return to the region with PWATs soaring to ~2 inches. As a result, the typical summertime afternoon convection will make it's reappearance as well on Sunday (esp. across southeast Georgia). Thereafter, the chances for afternoon showers and thunderstorms should continue through the mid-to-late week. Some of these thunderstorms could be strong to severe depending on how much instability can build each afternoon before the seabreeze kicks into the region. 12Z model guidance seems to support a high CAPE, low shear environment throughout the week, meaning afternoon convection will likely be short-lived (pulse- like), rather than long-lived, organized convection. Therefore, the main threats with these thunderstorms will be damaging wind gusts and locally heavy rainfall.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions will prevail at CHS/JZI/SAV terminals through 18Z Saturday.

Extended Aviation Outlook: Afternoon showers and thunderstorms may bring brief flight restrictions late this weekend into early next week.

MARINE

Through Tonight: South/southeast winds along the western periphery of an Atlantic high will top out near 10-15 kt this afternoon and evening (near the land/sea interface), then eventually turn south- southwest late. Seas will average between 2-3 ft.

Saturday through Tuesday: As an upper-lvl ridging slowly breaks down over the holiday weekend, weak troughing will develop across the waters on Sunday. Southwesterly flow should persist across the Atlantic in the early morning of the 4th, before switching around to south-southeasterly in the early afternoon. This set-up will yield a typical summertime pattern for the waters as the highest winds will be located along the land/sea interface each afternoon as the seabreeze forms and pushes inland. It's possible to see gusts 22-23 kt along the immediate coastline + across the local waters (including the Charleston Harbor) as this happens. Expect the winds to slightly veer each night through this period, but should be south-southeasterly throughout the daylight hours. Seas will range from 2- 3 ft on Saturday and Sunday, before increasing to 3-4 ft on Monday and Tuesday.

CLIMATE

Record High Temperatures:

July 3: KCHS: 98/2019

July 4: KCHS: 98/2023 KCXM: 98/1902 KSAV: 99/1997

July 5: KCHS: 100/1993 KSAV: 100/1902

July 7: KCHS: 99/1954

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

July 8: KCXM: 83/2016 KSAV: 80/1990

July 9: KCHS: 80/1998 KSAV: 80/1883

CHS WATCHES/WARNINGS/ADVISORIES

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