An atmospheric river will slam Florida and the Southeast with torrential rain

Atmospheric rivers are more typical in the West, but this one may bring flooding rainfall and severe storms to the Southeast, Florida and southern Appalachia.

By Ben Noll / Courtesy Washington Post

An atmospheric river will form in the Gulf of Mexico this weekend before slamming into Florida, the Southeast and southern Appalachia. Severe thunderstorms are possible in the area, and as the storm could fuel more than a half-foot of rain through early next week, there’s also a risk of dangerous flooding.

Atmospheric rivers — like rivers in the sky — are common along the West Coast during winter. But this one will take a less typical path from the western Caribbean Sea to southern states. Rainfall totals of 3 to 6 inches are expected, with totals of 6 to 10 inches possible in the most persistently rainy spots, while localized downpours of more than 10 inches can’t be ruled out. The worst of the storm will probably hit on Monday and Tuesday.

Florida, Georgia, South Carolina and North Carolina will probably be hardest hit by dangerous downpours, including in some of the same places hit by deadly Hurricane Helene last year.

While precipitation is generally needed in these places because it will help with drought conditions and reduce wildfire risk, this storm will bring rain that falls hard and fast, leading to a risk of flooding.

The disturbance driving the downpours formed part of an unusual weather phenomenon called an omega block, which drenched the southern Plains, Gulf Coast and Northeast earlier in the week.

Where and when rain will fall hardest

Rain and thunderstorms will become more widespread along the Gulf Coast this weekend, before strengthening into an atmospheric river and stretching into the Southeast, Florida and southern Appalachia through early next week.

Here’s a breakdown of where the most dangerous downpours are forecast to be each day.

Saturday

Slow-moving, heavy rain and thunderstorms are forecast across northern Florida and especially the Panhandle area, as well as Alabama, Georgia and South Carolina.

Cities where rain may be heaviest include Tallahassee and Jacksonville in Florida; Valdosta, Savannah, Macon and Atlanta in Georgia; and Birmingham in Alabama.

Sunday

Heavy rain and storms will continue to affect many of the same states and cities as mentioned above, but also more of South Carolina, southern North Carolina and central Florida.

Additional cities to be affected may include Charleston and Myrtle Beach in South Carolina, Wilmington in North Carolina and Gainesville, Orlando and Tampa in Florida.

Monday

The atmospheric river will probably reach peak intensity, bringing a volatile day of downpours, including possible flash flooding from Florida to western North Carolina as well as thunderstorms capable of producing waterspouts, tornadoes and damaging wind gusts.

Cities currently in the highest-risk zone include Tampa, Sarasota, Fort Myers, Orlando, Jacksonville, St. Augustine, Daytona Beach and Melbourne in Florida; Savannah, Augusta and Atlanta in Georgia; Charleston, Myrtle Beach, Columbia and Greenville in South Carolina; and Charlotte and Asheville in North Carolina.

Tuesday

Heavy rain and storms may affect South Florida before gradually clearing away, but continue across the Carolinas and move into the Mid-Atlantic and Ohio Valley.

In the table below, explore how much rain is forecast in your county through Tuesday.

Early signs of hurricane season

Fueling the atmospheric river is an eastward-moving pulse of rain and clouds, called the Madden-Julian Oscillation, moving into the Caribbean Sea.

When these pulses arrive in a region, they create conditions conducive to storm formation by enhancing atmospheric spin and increasing moisture availability.

Marine heat-wave conditions, such as those in the Caribbean Sea, can cause these storm-sparking features to focus over a particular area — and provide extra fuel for the upcoming atmospheric river.

While this early pulse is unlikely to spark a hurricane, it is perhaps an early signal that the waters south of the United States could be more unsettled this year and that coastal residents should be prepared for hurricane season, beginning June 1.