textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12Z TAFs.

KEY MESSAGES

- 1) Dangerous heat across portions of southeast Georgia and the South Carolina Lowcountry this afternoon. A few strong to severe thunderstorms are possible near the sea breeze this afternoon into early this evening.

- 2) Hot and humid conditions will persist through much of the week.

- 3) Typical summertime convection returns this week.

DISCUSSION

KEY MESSAGE 1: Dangerous heat across portions of southeast Georgia and the South Carolina Lowcountry this afternoon. A few strong to severe thunderstorms are possible near the sea breeze this afternoon into early this evening.

Sunday: The forecast area will remain between a mid-level trough over the Mississippi River Valley and a 592 DM ridge centered over the Bahamas. At the sfc, a broad trough will remain across the middle Carolinas through this afternoon. Given strong insolation and very warm llvl thicknesses, temperatures are forecast to exceed 90 by late this morning, then peaking in the mid to upper 90s. Recent runs of the HRRR, indicates that a sea breeze will develop during the mid-day, then pushing inland through this afternoon. Sfc dewpoints in the wake of the sea breeze should increase into the mid to upper 70s. There appears to be a couple of hours heat index values around 108 across the coastal counties of SC/GA. Highlighted with a Heat Advisory from 11 AM until 7 PM.

Hot and humid conditions will likely result in SBCAPE values to increase between 2000-3000 J/kg, potentially up to 3500 J/kg across portions of the SC Lowcountry. In addition, DCAPE values may pool in excess of 1000 J/kg across portions of the CWA this afternoon. High resolution guidance indicate that thunderstorms may develop along and near the sea breeze this afternoon. Coverage of thunderstorms may remain the greatest across the SC Lowcountry, primarily from Colleton County north to the Santee River. Moderate instability and weak shear may support some strong to severe pulse-type thunderstorms this afternoon and evening, with localized wind gusts. It is possible that the strongest updrafts will require a Severe Thunderstorm Warning or two. HREF indicates that PW values will increase to around 2 inches east of the H5 trough. The deep moisture and slow storm motions could result in some storms near the sea breeze to produces pockets of 2-3 inch rainfall. The thunderstorms should bring some relief from the heat late this afternoon.

KEY MESSAGE 2: Hot and humid conditions will persist through much of the week.

Temperatures will remain above normal this week, with highs generally peaking in the mid to even upper 90s in spots. Combined with elevated humidity, it will feel even hotter. Heat indices over 100F are expected each afternoon, with areas closer to the coast generally in the 105-110F range. Additional Heat Advisories will be possible, especially in the first part of the week. It's worth noting that with showers and thunderstorms back in the forecast, any convection that develops would limit the duration where heat indices reach the 108+ criteria. Regardless, this extended stretch of hot and humid conditions will bring a risk of heat-related impacts, especially to those more vulnerable to heat or those without adequate cooling/hydration.

KEY MESSAGE 3: Typical summertime convection returns this week.

A more typical summertime convective pattern is expected this week, with daily shower and thunderstorm chances. Coverage will be highest in the afternoon and early evenings, before dwindling after sunset with loss of insolation. Environment favors mainly pulse-type convection, however isolated strong to severe storms are possible with damaging wind gusts as the primary hazard. This jives with some of the AI/MLP guidance as well. Locally heavy rainfall is possible in any storms with PWats near or over 2", but flooding risk looks low especially given the hot and dry conditions of late.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

12Z TAFs: VFR conditions with light winds this afternoon. A sea breeze is timed to push across KJZI by 16Z and KCHS and KSAV by 17Z, resulting in south winds around 10 kts. Scattered to numerous thunderstorms are forecast to develop near the sea breeze between 19-23Z, highlighted with TEMPOs at each terminal. Convection should decrease this evening.

Extended Aviation Outlook: Brief flight restrictions are possible in afternoon showers/thunderstorms this week.

MARINE

Today through tonight: The pressure pattern should support south winds between 10 to 15 kts, with occasional gusts to 20 kts. Wave heights are forecast to favor 3 ft today, increasing to 3-4 ft.

Monday through Friday: A fairly typical summertime pattern on tap for this week. Southwest winds in the morning will back more to the south for the afternoon and evenings. Speeds are forecast to stay below Small Craft Advisory criteria through the period, however gusts in the low 20 kt range are possible, especially in the afternoon and evenings. Seas will average 2-4 feet.

CLIMATE

Record High Temperatures:

July 5: KSAV: 100/1902

July 7: KCHS: 99/1954

July 10: KCHS: 100/1986 KCXM: 99/1986

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

July 10: KCHS: 81/1986 KCXM: 82/1986

July 11: KCHS: 80/2016 KCXM: 82/2016

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for GAZ217>219-239>241. SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for SCZ045-148>152. MARINE...None.