Messages

1) Strong to severe thunderstorms are possible this afternoon and again Monday afternoon.

2)Increasing rain chances mid to late week with the potential for locally heavy rainfall.

Discussion

KEY MESSAGE 1: Strong to severe thunderstorms are possible this afternoon and again Monday afternoon.

The synoptic pattern aloft today and tomorrow will be similar, featuring large scale troughing along the eastern CONUS. A weak surface front will linger in the vicinity of the SC Midlands into the middle of the week. Shortwave troughs are expected to ripple across the southern periphery of the large scale troughing aloft today and Monday. This synoptic set up will allow for strong to severe thunderstorms to develop both this afternoon and again Monday afternoon.

Today: Plentiful dry air aloft was observed with the 12Z KCHS weather balloon data sounding, yielding a precipitable water value of 1.47". precipitable water this afternoon are only forecast to increase slightly across the region, in the 1.5 to 1.6" range. This will limit the overall heavy rain threat today. However, with the dry air aloft the 12Z sounding this morning also observed a DCAPE value of 1100 J/kg. DCAPE values this afternoon are forecast to increase upwards of 1500 J/kg. Damaging wind gusts will be a threat with any storm that is able to form this afternoon. Machine learning guidance for this afternoon depicts the main threat area across the SC Lowcountry. Current GOES satellite imagery shows a rather agitated cumulus field across the SC Lowcountry and the KCLX radar has detected the first shower of this afternoon as of 2 PM in northern Charleston County. As the sea breeze progresses further inland and additional outflow boundaries interact isolated to scattered thunderstorms are forecast this afternoon. The entire forecast area remains outlooked in a Marginal Risk (Level 1 of 5) from the Storm Prediction Center. Thunderstorm activity will wane with nightfall.

Monday: Forecast soundings paint a similar picture to Sunday on Monday afternoon, however with precipitable water increasing to around 1.7 to 1.8". Coverage of thunderstorms is forecast to be greater, with scattered to numerous chance of rain in the forecast. DCAPE values are still forecast to be upwards of 1500 J/kg. Damaging wind gusts will again be the main hazard. Machine learning guidance shows the main threat area across SE Georgia, with slightly higher probabilities of damaging wind gusts than portrayed on Sunday. The current outlook from the Storm Prediction Center is another Marginal Risk (level 1 of 5).

KEY MESSAGE 2: Increasing rain chances mid to late week with the potential for locally heavy rainfall.

Wednesday through Thursday, the region will remain between a Bermuda high and low pressure over the Southern Plains. This pattern should support steady southwest H85 winds across the Deep South and Southeast U.S., aiding in rising PW values across the region. By Thursday, the American global model forecast soundings indicate PW values exceeding 1.9" across SE GA and SC. As temperatures warm into the low to mid 90s, a sea breeze should develop each afternoon, pushing inland through the early evening hours. Instability could pool into moderate levels given dewpoints in the upper 70s to near 80 degrees. The forecast will indicate scattered to numerous chance of rain for showers and thunderstorms.