A sprawling storm system coming out of Mid-South is set to drench parts of the eastern United States with heavy rain while generating gusty winds and coastal flooding. Severe thunderstorms are also possible across the Gulf Coast and Southeast just a day after a swarm of tornadoes tore through the Texas and Louisiana Golden Triangle.
The National Weather Service Storm Prediction Center declared a level 2 out of 5 threat of severe weather in the Southeast Thursday, noting that “damaging winds and a few tornadoes will be possible.” The risk area stretches from South Florida up the Interstate 95 corridor into the eastern Carolinas, including Jacksonville, Tampa, Savannah, Charleston and Wilmington, N.C.
A tornado watch is in effect over the central part of the Florida Peninsula until 5 p.m. Thursday, with a “moderate” chance that two or more tornadoes touch down.
Coastal flood advisories and warnings span much of the Mid-Atlantic coastline, meanwhile, with a storm surge or rise in water above normally dry land of 2 to 4 feet anticipated Friday. That will be in addition to sporadic instances of inland flooding, the rain coming down on already-saturated soils stemming from months of above-average rainfall.
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On Thursday, the storm center was located near the Arkansas-Missouri border. It was shifting east toward Middle Tennessee. By early Friday, it will transfer its energy to West Virginia before slowly weakening over the central Appalachians.
Attached to the storm center was a cold front that stretches southward into the Gulf of Mexico, ahead of which warm, moist air was being scooped northward. The humid air was feeding showers and storms clustered over Georgia, the Carolinas and Florida. To the north, a slug of downpours was spiraling toward the storm center.
On the cool side of the system, a few additional showers were swirling back in the “comma head” of the storm over Illinois, the Corn Belt and the Ozarks. That rainfall will be mainly light.
Daytime heating ahead of the cold front in Florida and in eastern parts of Georgia and the Carolinas will destabilize the atmosphere, bolstering the propensity for air to rise into strong to locally severe thunderstorms on Thursday. A change in wind speed and/or direction with height, known as wind shear, will also foster rotation in a few of the storms.
Meteorologists are expecting a squall line to form with embedded circulations, any of which could produce a quick-hitting, short-lived tornado. That setup is referred to as a QLCS, or quasi-linear convective system.
Ahead of the line, more isolated, discrete rotating supercell thunderstorms are possible. Those pose an increased risk of tornadoes that could spend a bit more time on the ground and be stronger. That proved instrumental in Wednesday’s significant tornadoes in Louisiana and the Texas Golden Triangle.
Thursday night through Friday
That batch of storminess will last between 6 and 10 hours in most locations, progressing northeast up the coast Thursday evening and soaking the Mid-Atlantic on Friday.
Washington and Baltimore will see steady rain shortly after sunrise Friday, becoming moderate to heavy at times during the late morning and early afternoon before tapering off in the evening or first part of the overnight. A general 1 to 2 inches is possible.
As the storm draws winds from east and southeast in the Mid-Atlantic, coastal waters will pile up along the shorelines, leading to flooding. Coastal flood warnings are in effect Friday into Saturday for up to 2 to 4 feet of inundation. The National Weather Service in Washington and Baltimore tweeted this storm could bring “one of the biggest tidal flood events of the past 10-20 years,” affecting places like Annapolis, the southwest Washington waterfront and Alexandria.
The warm, humid air should not make it much past the Virginia-North Carolina border, so regions from the Tidewater northward probably won’t see any severe weather.
Throughout the Mid-Atlantic and Northeast, it will also be quite windy with gusts reaching 30 to 40 mph Friday and Saturday; however, gusts won’t approach the level from the midweek bomb cyclone that unleashed gusts over 40 mph in the Mid-Atlantic and 90 mph in eastern New England.
Friday night into Saturday
New York City can expect a wet Friday night, the timing likely to interrupt any evening plans residents may have. Downpours will arrive into southern New England later on Friday and into Saturday.
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Meanwhile, parts of the Deep South are cleaning up from a localized swarm of fierce tornadoes that touched down in extreme East Texas and southwest Louisiana on Wednesday. One tornado touched down in Lake Charles, La., a city that saw 135 to 150 mph winds from Hurricane Laura last August before being hit by Delta less than two months later and a crippling ice storm in February.
“It’s been a rough period,” said Rua. “I can say living in Lake Charles, it’s been rough basically starting with Laura, obviously Delta, then into the wintertime. We also had a 20-inch rain event back in May.”
Rua noted that the Lake Charles tornado, officially rated an EF2 with 130 mph winds, formed from the squall line. “Significant structural damage” occurred to several homes during the twister’s 2.2-mile jaunt through neighborhoods, with a pair of injuries reported.
“The one in southwest Louisiana was a QLCS type,” said Rua. “It’s very rare for the Lake Charles area to get an EF2. The last time we got an EF2 in Calcaseiu [Parish] was in 1999.”
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Another tornado crossed Interstate 10, tossing a vehicle as a dense cloud of debris floated around the voracious funnel. Forecasters are still surveying the damage to determine the twister’s rating.
“They’ll be going out and doing more surveying,” said Rua. “That’s the one they still haven’t finished up on yet, but I think they’re going to rate it as an EF2 also. This one had a longer track, so it’s probably going to do more significant damage.”
Rua said that southwest Louisiana doesn’t have as crisp or neatly-bounded of a tornado season as places like, for example, Oklahoma, due to the Bayou State’s proximity to warm Gulf waters.
“Basically we have, if it’s a stronger tornado, two time periods,” he said. “Either late fall and early winter from the end of October into the first part of December, or once again we have more in late February into March.”
The same storm system also spawned tornadoes in Oklahoma early Wednesday, including one in the city limits of Norman northeast of the University of Oklahoma.
The strange, energetic storm system was born of a symphonic display of meteorological chaos that featured a record-setting “double bomb” cyclone in the Northeast Pacific over the weekend. That steered ashore a top-tier atmospheric river into California, which dropped record rainfall totaling 6 to 12 inches and also achieved moisture records.
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The atmospheric river, which demarcated a cold front, swept east, a new area of low pressure forming along it over the Four Corners on Monday. By Tuesday, moisture from Hurricane Rick, which made landfall Monday as a strong Category 2 near Lazaro Cardenas, Mexico, was being drawn into heavy downpours in Texas. Its leftover spin also proved crucial to enhancing tornado chances near the Texas-Louisiana border.
Jason Samenow contributed to this story