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The Weather Prediction Center's Excessive Rainfall Outlook for today with South Carolina in focus.
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The Severe Weather Outlook for today from the Storm Prediction Center (SPC)with South Carolina in focus.
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True Color visible satellite imagery from this morning centered on the Southeast, showing clusters of thunderstorms moving toward South Carolina. (Photo by University of Wisconsin RealEarth)
We have an unusual weather situation over the Palmetto State today leading to a risk of severe thunderstorms for much of the state. The last cold front that moved through back on Sunday and Monday is retreating northward as a warm front today. Meanwhile, the upper-level wind is stronger than usual over this part of the nation and roughly parallel to the front. Upper-level disturbances are triggering clusters of thunderstorms to our west that are moving this way, which you can see on satellite imagery.
The first is moving into the state as of late morning. It will produce a round of heavy rainfall, mainly over the Lowcountry. The severe storm risk is low with the first wave of thunderstorms, except in the Lowcountry, where storms have a better chance to cause damaging wind and hail. Behind this first round of thunderstorms, warm and muggy air will surge northward into more of South Carolina, setting the stage for more intense storms later today and tonight.
The second round of storms likely gets going late this afternoon and continue through this evening. Once again, the focus will be on the Lowcountry, but some of the Central Savannah River Area and Midlands will get in on the action. The main concern for the storms will be damaging wind, which may be widespread over the southernmost part of the state. This is because of the unusually strong wind aloft; thunderstorm downdrafts can pull the momentum of these strong winds to the surface. There can also be hail large enough to cause damage (the threshold for 'severe' hail is one inch in diameter), and there is a chance for an isolated tornado or two.
Areas farther north might see an isolated severe storm with damaging wind and hail. However, clouds and rain from the first round of thunderstorms should keep this area cool enough to limit the severe storm potential from later rounds of storms.
A third round of storms will affect parts of the state later tonight. The worst of this will hopefully pass mainly to our south and we can also be hopeful that the late-night timing leads to less instability and less intense storms. You'll still want to be ready for severe storms if you're in the Lowcountry, though. If this is where you'll be tonight, be sure you have a way to be alerted for any warnings that will wake you up. Risks will include damaging wind, hail, and an isolated tornado or two.
As you can see from SPC's outlook, the farther south you are today and tonight, the greater your risk is of seeing severe storms.
The main area of concern for severe storms is to our southwest, from northern Louisiana to southern Georgia. If you're traveling that way, be ready to encounter severe storms that can cause widespread damaging wind and hail along with isolated tornadoes. When you must travel through a severe weather minefield, you'll want to keep up with which county you're in and have your phone's severe weather notifications set to alert for your current location. Take a break from driving when severe storms are bearing down on you, and find a sturdy building to ride out the storm.
In addition to the wind, hail, and tornado risks, the storms are tapping into tropical moisture and will bring heavy rainfall. Again, the farther south you are, the greater the risk of seeing enough rain to cause flash flooding. The risk is highest over Jasper and Beaufort Counties, which have the best combination of wet soil from recent rainfall and heavy rainfall potential through tonight.
The front will sink back to the south tomorrow, but the Lowcountry will remain unsettled with more thunderstorms. The severe storm risk is low, though. Friday looks active statewide as another cold front moves in from the north to trigger a scattering of thunderstorms, but the severe storm potential again looks low.