textproduct: Charleston

WHAT HAS CHANGED

Area of greatest heavy rainfall threat this afternoon has been refined to near and south of Hinesville.

The likelihood for hazardous heat on Monday has diminished.

KEY MESSAGES

- 1) Localized flash flooding and damaging wind gusts possible for portions of Southeast Georgia through early evening. - 2) A fairly typical summertime pattern is expected with daily shower and thunderstorm chances.

- 3) Hot and humid conditions likely to peak Tuesday.

DISCUSSION

KEY MESSAGE 1: A weak front continues to slowly slide southward, pushing just south of I-16 early this afternoon. This front will likely stall and wash-out through the rest of the day, but has already positioned the band of primary moisture convergence across Southeast GA, where PWAT values have surpassed 2 inches and MLCAPE is approaching 2000 J/kg.

Storm motion is likely to be mostly eastward at 20+ mph. The concern is that the cold pool building into the westerly shear will result in training storms, which could bring multiple rounds of downpours near or south of the front. Guidance continues to focus on areas from around Hinesville southward for the greatest persistent heavy rainfall threat, with probs for greater than 2 in of 50-60% and probs for greater than 3 in of 20-30% across the corridor from Hinesville to Brunswick.

Convective activity is expected to wane by/around sunset with the loss of peak instability. While debris clouds/cirrus will likely persist through much of the night, there is a low chance that there will be sufficient radiational cooling to develop some shallow fog early Sunday morning where rain falls this afternoon.

KEY MESSAGE 2: A fairly typical summertime pattern is expected with daily shower and thunderstorm chances.

The mid-levels will consist of a series of weak disturbances moving over the Southeast the next few days. At the surface, areas of High pressure will be in the eastern Gulf and the Atlantic, while fronts should generally remain just to our north. Additionally, there should be weak surface troughing over our region at times. The combination of moisture across our region and instability generated from the typical June high temperatures will generate showers and thunderstorms. Isolated showers and thunderstorms are possible on Sunday, with the coverage increasing to scattered Monday and afterwards. Showers and thunderstorms are expected to peak in the late afternoon and early evenings, when instability is at its highest. The threat for organized severe weather is low, but we cannot rule out a couple of strong to severe storms each day.

KEY MESSAGE 3: Hot and humid conditions likely to peak Tuesday.

High temperatures are forecasted to peak in the lower to middle 90s on Tuesday. Combined with dew points in the 70s, heat index values should exceed 100 degrees across much of our area. The highest values will be along the coastal sea breeze, where dew point pooling is expected. This will equate to heat index values peaking in the 105-110 degree F range. We need heat indices of 108 degrees F for at least 2 hours to prompt a Heat Advisory. However, the hourly forecast values indicate this is very borderline. Additionally, afternoon convection will quickly lower heat indices. So we cannot rule out Heat Advisories for a short time period near the coast.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

20/18z TAF Discussion: A weak front pushing south will help focus shower and storm activity across SE GA late afternoon through early evening. While the majority of the storms are expected to remain just south of SAV, a passing storm or two could bring brief restrictions and gusty erratic winds to the terminal. Further north, dry mid-level air will limit storm chances, with VFR prevailing at CHS/JZI this afternoon and evening. VFR then prevails at all terminals overnight into Sunday.

Extended Aviation Outlook: Brief flight restrictions are possible with any showers and thunderstorms.

MARINE

Through Tonight: Breezy post-seabreeze winds nearshore continue through early evening, with light winds prevailing tonight. A few storms could push off the GA coast later today, bringing locally gusty/erratic winds. Otherwise, seas subside to 1-2 ft overnight, overall excellent marine conditions for this time of year.

Sunday through Thursday: The only marine concern is the synoptic setup could cause a surge of SW winds Tuesday afternoon and evening. Gusts could approach 25 kts at times, especially for the Charleston County waters. But it looks very marginal for Small Craft Advisories at this time. Otherwise, the rest of the time period will consist of a typical summertime wind regime.

CLIMATE

Record High Minimum Temperatures:

June 23: KCHS: 78/2024 KSAV: 77/2017

CHS WATCHES/WARNINGS/ADVISORIES

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