The sweltering heat and humidity that boosted heat indices over 115 degrees in parts of the Lowcountry over the weekend is about to be a thing of the past. Heavy rain and the flash flood potential from thunderstorms are about to be a thing of the present and future thanks to a change in the weather pattern over the state.
The large ridge of high pressure from the Southeastern United States to the Central and Southern Plains is retreating. In its place, a trough of low pressure is digging southward from the Tennessee Valley into the eastern Gulf of Mexico. The resulting wind pattern from the southwest out of the Gulf of Mexico will spread copious moisture northward into the Palmetto State.
The heaviest rain is most likely along and to the south of a stalling cold front over the state. The Lowcountry is therefore in line to see the most rain this week, but locally heavy rainfall is also likely as far north as the Upstate for a time on Tuesday. Longer-range computer models are forecasting the front to hang around through Friday, which heightens the threat of flooding.
Average rainfall of 4 to 7 inches is forecast this week from the Grand Strand to the Lowcountry, with amounts tapering with northward and westward extent. 1 to 3 inches of rain are expected over the Upstate. These amounts are enough for scattered areas of flash flooding, particularly with much of the state receiving 50 percent more than average rainfall so far this summer.
