The powerful storm system that has prompted Tornado Watches over a wide area from east Texas to Alabama Wednesday afternoon and evening is expected to threaten the Palmetto State on Thursday.
The National Weather Service's Storm Prediction Center -- who is responsible for storm outlooks across the United States -- has assigned their highest rating, a level 5, for much of Mississippi and Alabama into Wednesday night. They have upgraded much of South Carolina to a level 4 on Thursday, which means atmospheric conditions are likely to be conducive for a regional outbreak of damaging winds, tornadoes, and hail.
A line of the thunderstorms is forecast to approach Pickens, Oconee, Spartanburg, and Greenville counties between sunrise and mid-morning. The fast-moving line is likely to approach the Rock Hill area during the late morning, the Midlands and Central Savannah River Area (including Columbia and Aiken) around midday or early afternoon, and the Pee Dee and Lowcountry during the middle of the afternoon. Finally, the Grand Strand is likely to see the storms arrive during the late afternoon hours. The cold front that is partially responsible for the storms will sweep offshore, taking the threat of severe weather offshore around sunset or shortly thereafter.
2PM Update: Thursday's severe weather risk remains largely unchanged. Entire forecast area remains in a moderate (level 4/5) risk for severe weather. Widespread damaging wind gusts, a few tornadoes (some strong) and large hail are all possible mainly tomorrow afternoon. #caewx pic.twitter.com/DnzQOKEnwK
— NWS Columbia (@NWSColumbia) March 17, 2021
Strong wind shear, which is an increase in the wind speed or a change of wind direction as one goes above the ground, is forecast to be favorable for straight-line damaging winds and a few strong tornadoes. These hazards are possible anywhere in the state on Thursday, but high-resolution models as of midday Wednesday have suggested the Midlands, Lowcountry, and Pee Dee areas could have a slightly greater potential for rotating storms. Hail the size of quarters or larger are also possible with the strongest thunderstorms.
South Carolinians are strongly encouraged to have multiple ways to receive trusted weather watches and warnings on Thursday. NOAA Weather Radio and local broadcasters often provide the most relevant, up-to-date information based on their knowledge of the local geography and meteorology. Remember, a Tornado Watch is often issued first, and is the initial indication that tornadic storms are possible. Tornado Warnings are issued normally a few minutes before a tornado is in your area and are your indication protective action is needed. Meteorologists strongly recommend having a plan of action when watches and warnings are issued for your area. As a reminder, the lowest-level of a well-built home or business, away from windows and exterior walls, is the safest place to shelter. Those living in mobile homes should have a plan to seek sturdier shelter before a tornado warning is issued.
