textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Isolated to scattered thunderstorms are expected to develop along the sea breeze this afternoon. These thunderstorms will be capable of producing gusty winds, locally heavy rainfall, and cloud to ground lightning.

DISCUSSION

KEY MESSAGE 1: Isolated to scattered thunderstorms are expected to develop along the sea breeze this afternoon. These thunderstorms will be capable of producing gusty winds, locally heavy rainfall, and cloud to ground lightning.

Overall, the surface pattern across southeast GA and southeast SC will be rather diffuse today. This should allow the sea breeze circulation to take shape in the early afternoon and begin to gradually push inland. Somewhat similar to yesterday, dewpoints across the inland tier of the area will be on the low side and are forecast to mix out into the low to mid 60s. However, along the coast low to mid 70s will be more common and should provide sufficient low-level moisture to allow for convective initiation along the sea breeze. Hi-res model solutions and the 31/00z HREF all paint a similar picture with scattered coverage along the coastal corridor where the best moisture pooling will reside. Model soundings show a pretty typical summertime environment. Instability is modest, with MLCAPE values on the order 1,500-2,000 J/kg, owing to warm mid- levels and weak lapse rates. However, there will be plentiful mid and upper level dry air which will yield DCAPE values well in excess of 1,000 J/kg. Also, wind profiles are weak and will favor storm motion of no more than 10 knots. So, instability will likely be a limiting factor and help keep the overall severe threat low, but it is possible we could see a couple of quick pulsing storms capable of producing damaging wind gusts. Also, with minimal storm motion there is the potential for locally heavy rainfall. Convection will likely struggle to spread inland thanks to the aforementioned lower dewpoints. Storms should mostly run their course by the late afternoon and steadily dissipate through the early evening hours.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

The 12z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. Satellite imagery and surrounding observation do show there is some MVFR/IFR stratus near KSAV. This stratus could spread into the terminal over the next 1-2 hours, but even if it does it will be short-lived. The main forecast issue will come this afternoon with the potential for thunderstorm develop along the sea breeze. This will put the development zone in the vicinity of all 3 terminals. There is very little confidence on the exact placement of storms this afternoon, but the overall thinking is for isolated to scattered storms along the coast starting around 17-18z and continuing through 20-21z. Thereafter the potential for storms will wane and the rest of the period should be free of thunderstorms. We have maintained a PROB30 for this time period at all 3 sites, with a slightly earlier shift in timing for KJZI. If storms directly impact the terminals, gusty winds will be possible along with MVFR/IFR visibility in heavy rainfall.

Extended Aviation Outlook: The probabilities for periodic flight restrictions due to showers and thunderstorms will increase this weekend into early next week.

MARINE

Today and tonight: A stationary front will stretch across the Southeast and extend into the local waters through tonight. This will support relatively light winds with seas generally around 1 to 2 ft.

A strong cold front is expected to approach from the west later this weekend, causing winds and seas to build as the pressure gradient tightens. Wind gusts of 25-30 kt are possible across portions of the local waters on Sunday, with seas increasing to 5 to 6 ft. Small Craft Advisories could be needed. Marine conditions are expected to gradually improve Monday into Tuesday as the front weakens/moves out of the area.

CLIMATE

Record High Minimum Temperatures:

August 1: KSAV: 79/2020

August 4: KSAV: 78/1941

August 5: KCHS: 79/1980 KCXM: 82/1991

CHS WATCHES/WARNINGS/ADVISORIES

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