The potential for strong thunderstorms and heavy rainfall returns to the Southeast after an already active week of violent weather. The storm setup is forecast to be similar to the previous system which moved through parts of the Palmetto State last Monday. Similar hazards such as damaging winds, small hail, and isolated tornadoes will be possible beginning Thursday.
A deepening low pressure system over the north central Gulf of Mexico Wednesday was tracking onshore across the Florida Panhandle and into Georgia. This low pressure will continue through the Mid-Atlantic Thursday while dragging a strong cold front to the southwest of the system.
Ahead of this storm system, warm and rich moisture from the Gulf will spread northward into the Southeast which will fuel shower and thunderstorm development. The highest moisture and instability is expected to favor southern locations in the Lowcountry which should provide enough energy to produce a few isolated strong to severe thunderstorms throughout Thursday.
The Storm Prediction Center Wednesday issued a Slight Risk (hazard level 2 out of 5) for parts of extreme southeast parts of the Lowcountry, including Hilton Head Island. A Marginal Risk (hazard level 1 out of 5) extends north and west through the remainder of the Lowcounty and Pee Dee. This encompasses the cities of Charleston and Myrtle Beach.
Showers and thunderstorms will begin lifting in from Georgia beginning pre-dawn Thursday before becoming more widespread through the rest of the day across the Palmetto State. Rounds of rainfall are likely throughout the day Thursday and into the overnight as the low pressure system and the associated cold front crosses through the Carolinas and exits out into the Atlantic.
The National Weather Service in Columbia Wednesday afternoon issued a Flash Flood Watch from 1AM EST Thursday through Friday morning for central and eastern parts of the Midlands and western portions of Pee Dee and the UpState.
Soils remain saturated from the previous storm system earlier in the week and the chance of flooding has increased ahead of this next system. According to the National Weather Service in Columbia most of central South Carolina and the Central Savannah River area have experienced 300 to 500 percent of normal rainfall over the past week.
Additionally, parts of northwestern South Carolina could experience a taste of winter weather as the low pressure lifts through the region. A Winter Weather Advisory has been issued for northern locations of the UpState and the Midlands Wednesday evening through Thursday night, which includes the cities of Spartanburg and Greenville. Freezing rain is possible as temperatures hover near freezing during the overnight into Thursday. A few isolated locations could experience brief snowfall. Temperatures will gradually warm throughout Thursday morning transforming the ice and snow back to rain. However, higher elevations could remain below freezing throughout Thursday, keeping the chance for ice and mixed precipitation possible.
Upon the passage of the cold front, drier air and clear skies will return as high pressure build in from the west. Breezy winds are expected behind the frontal boundary with overnight temperatures dipping to below freezing Friday night and Saturday night in the UpState and Midlands. Near freezing conditions possible out to coastal portions of Pee Dee. Warmer overnight lows in the upper 30s to lower 40s in the Lowcountry expected.