The majority of South Carolina will be in the path of a strong storm system Thursday which could produce multiple hazards including damaging wind gusts, large hail, and tornadoes.
A formidable low pressure system over the central Mississippi Valley and its associated cold front, extending southwards into the Gulf of Mexico, was producing a significant outbreak of tornadoes, damaging winds, and hail over parts of Alabama, Mississippi and Georgia Wednesday. The National Weather Service's Storm Prediction Center (SPC) Wednesday issued the maximum hazard alert-- a High Risk-- for a large portion of central Mississippi and Alabama. Numerous strong and a few long-track, potentially violent tornadoes, are expected to continue into the overnight Wednesday with the threat shifting east into the Palmetto State Thursday morning.
The latest update from the SPC continues to place the majority of South Carolina in a Moderate Risk (hazard level 4 out of 5) for Thursday, which means atmospheric conditions are likely to be conducive for a regional outbreak of damaging winds, hail, and tornadoes, some of which could be strong and long-tracking.
A line of thunderstorms ahead of the strong cold front is forecast to move into the Upstate and approach Pickens, Oconee, Spartanburg, and Greenville counties between sunrise and mid-morning. The fast-moving line of showers and thunderstorms is likely to approach the Rock Hill area towards 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 majority of the storms is forecast to exit offshore into the Atlantic around sunset and into nightfall.
Here are the estimated times of arrival for storms over South Carolina:
- Grenville, Clemson, Anderson and Spartanburg areas: 6 - 11 AM EDT
- Laurens, Greenwood, and Union areas: 10 AM - Noon EDT
- Newberry, Chester and Rock Hill areas: 11 AM - 1 PM EDT
- Aiken, Columbia and Lancaster areas: Noon - 3 PM EDT
- Florence, Sumter, Orangeburg and Walterboro areas: 2 PM - 5 PM EDT
- Hilton Head, Beaufort, Summerville and Lake City areas: 4 PM - 6P M EDT
- Charleston, Georgetown, and Myrtle Beach areas: 5 PM - 8 PM EDT
Strong wind shear, which is an increase in the wind speed or a change of wind direction above the surface, is forecast to be favorable for straight-line damaging winds and a few strong tornadoes Thursday. These hazards are possible state-wide, but high-resolution models as of Wednesday evening continue to suggest that the Midlands, Lowcountry, and Pee Dee areas could have a slightly greater potential for rotating storms. Daytime heating will give strength to the line of storms as they move through parts of the Midlands in the afternoon which will aid in fueling thunderstorms and increase atmospheric instability. Quarter sized hail or larger will also be possible with the strongest thunderstorms.
Several school districts across South Carolina have announced closings for Thursday out of an abundance of caution. South Carolinians are strongly encouraged to review their severe weather plan and 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.