Thunderstorms capable of producing destructive wind gusts up to 70 mph are possible across a large area of the Palmetto State late Sunday night or Monday morning. A few tornadoes are also possible, along with heavy rainfall, ahead of a powerful cold front that is expected to move through Monday.
The storm system likely to affect the state is part of a larger weather system that is favored to produce long-track tornadoes, straight-line winds, and large hail from as far west as Texas through Deep South into Alabama, Georgia, and the Florida Panhandle Sunday afternoon and evening.
Reliable model simulations show much of the state receiving rain as soon as Sunday morning in response to a warm front moving northward from Georgia. Damaging thunderstorms are unlikely with this initial round of rainfall. Once the warm front moves into North Carolina, an increasingly humid and unstable air mass is likely to spread over South Carolina Sunday afternoon and Sunday night. The arrival of the worst weather is a bit uncertain and may change over the weekend, but present trends are pointing toward some time between midnight Sunday night and noon on Monday. Upstate residents would be the first to experience the thunderstorms, while residents of the Pee Dee, Lowcountry, and Grand Strand are more likely to see the weather some time Monday morning.
One of the most striking features of this large storm is the amount of wind expected from it. Wind speeds at an elevation of a few hundred feet above the ground are forecast to be in excess of hurricane force. Thunderstorms often act as a mechanism to transfer these strong, damaging winds toward the ground. For this reason, straight-line winds would be the primary hazard. If other atmospheric ingredients, such as sufficient moisture and instability are realized, then a few tornadoes are also possible.
NOAA’s Weather Prediction Center says rainfall amounts of 3 to 6 inches are expected starting Sunday and lasting into Monday, especially over the Upstate. The agency issued a "moderate risk" (a level 3 out of a possible 4) for flash flooding. Normally, it assigns this risk when numerous instances of flash flooding are likely. Lesser amounts of rain are forecast over the Midlands, Lowcountry, and Pee Dee, but pockets of flash flooding are still possible in those areas.
Not to be overlooked, but the portion of the #Upstate of #SouthCarolina near the Escarpment have a level 3 (out of 4) risk for flash flooding on Sunday. Rain likely to start in the morning; severe storms come much later (overnight Sunday). 3-5" of rain possible red areas. #scwx pic.twitter.com/L2oKcbiPSq
— Ray Hawthorne (@ray_hawthorne) April 10, 2020
Some parts of the state may see these damaging thunderstorms before the sun rises on Monday morning. Meteorologists and emergency management officials strongly recommend residents have multiple ways to receive warnings to increase your odds of receiving them. These include NOAA Weather Radio and Wireless Emergency Alerts (WEA) from your mobile device, as well as local radio and television stations.