For the second time in a week, a major outbreak of tornadoes is likely over the Deep South. This time, the threat of widespread severe weather is much lower in South Carolina, but a few stronger storm cells are possible Thursday afternoon through Friday.
A wave of showers and thunderstorms are likely Thursday afternoon into early evening over the Upstate, especially along and west of I-85. These storms will be tied to a warm front moving from south to north. The air is likely to be cool and stable north of the warm front much of the day, but locally heavy rain may produce areas of flash flooding in some of the hillier terrain. 1 to 2 inches of rain, with a few higher amounts, are possible with Thursday's rain and storms in this portion of the Upstate.
The center of low pressure that is responsible for the severe weather threat is over Arkansas Thursday morning. It is expected to track into Illinois and Indiana Thursday night before reaching the eastern Great Lakes Friday. The trailing cold front will sweep eastward across the lower Mississippi and Tennessee Valleys through Thursday night, and the greatest risk of tornadoes will be out ahead of the front. A combination of strong wind shear, unstable air, and rising air motion are the reasons why the environment is so favorable for tornadoes to our west.
As the cold front approaches the Upstate early Friday morning, the air will not be as unstable and the most significant rising air should stay west and north of the state. Still, strong wind shear may be enough to produce isolated reports of strong wind gusts or a brief tornado after midnight Thursday night until about sunrise Friday in the Upstate.
Daytime heating on Friday should enable the air to destabilize over the Midlands and Pee Dee. However, the wind shear and rising air motion will continue to weaken. These ingredients would suggest that one or two storms may become strong enough to produce gusty winds, but widespread reports of severe weather are unlikely.
The approach of another cold front on Sunday may produce strong thunderstorms over portions of the state, especially the Midlands and Pee Dee, but the location and timing of ingredients that normally cause severe thunderstorms may not line up. It is a good idea to check the forecast again on Sunday morning once there is greater certainty in the forecast.
