The Rain 'Machine' Affecting The South On Mother's Day Weekend

Forbes

10-05-2025

The Gulf Coast region and much of the southeastern U.S. is locked into a weather pattern that will bring rainfall to the region all weekend and into the first part of the work week too. Here's a meteorological explanation of the 'rain machine' affecting the Southeast this Mother's Day weekend.
The Scenario
NOAA's Weather Prediction Center wrote, 'A dawdling storm system along the Gulf Coast will generate rounds of heavy rain and thunderstorms this weekend and into the first half of next week." The culprit is an upper an upper-level low that is meandering over the Deep South, according to WPC. Meteorologically, there is plenty of Gulf moisture and a stationary front will also provide a source of 'lift' that could trigger thunderstorms daily. WPC noted, '…. An expansive Marginal Risk (threat level 1/4) for Excessive Rainfall that stretches from the Lower Mississippi River Valley to as far east as the Southeast coast each day this weekend.' WPC has issued a Slight Risk (threat level 2/4) for parts of the Florida Panhandle, Alabama, Georgia, and South Carolina.
By Sunday, the upper low will not have moved very much at all and will still be sitting over Louisiana. That cutoff low scenario provides a 'pump' of moisture into the Southeast. For most of us that means a wet Mother's Day. Let's further explore the meteorology of what's going on.
Risk of excessive rainfall on Mother's Day.
NOAA
What is a Cutoff Low?
The 'rain machine' that I am referring to is not some wacky conspiracy theory. As soon as I typed that my 'spidey senses tingled' because sadly there are fringe factions that may miss the metaphor. That's a slight digression, let's stay on task. University of South Alabama meteorologist Jordan McLeod nailed it. He called it, 'A classic cutoff low pattern in a transition season.'
The cutoff low over Louisiana on Sunday morning.
College of Dupage/NWS/NOAA
What is a cutoff low? The National Weather Service glossary defined it as, 'A closed upper-level low which has become completely displaced (cut off) from basic westerly current, and moves independently of that current. Cutoff lows may remain nearly stationary for days, or on occasion may move westward opposite to the prevailing flow aloft (i.e., retrogression).' That's what is happening in this scenario. The low in the graphic below is going to sit in the same spot for a few days before finally moving out during the middle of the week.
Meteorologically, the circulation around a 'low' is counterclockwise in the northern hemisphere. With the low positioned over Louisiana, moisture flow into the Southeast is coming from the Gulf region. In 2009, the Atlanta area experienced major flooding, and the culprit was a cutoff low situated to the west of Georgia. Our research group published an overview of that event in 2011. A 2025 study published in the journal Nature suggested that long-lasting cutoff lows will become more frequent in the Northern Hemisphere.
Is It An Atmospheric River in the South?
While the term 'atmospheric river' is more commonly associated with the West Coast, the water vapor metrics used to define them indicate that this is an 'atmospheric river' setup. NOAA defined atmospheric rivers as, 'Relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics.' Ben Noll described this weekend atmospheric river scenario in the Washington Post.
Though less common than western counterparts, atmospheric rivers in the Southeast do happen. Our research team at the University of Georgia, led by Dr. Neil Debbage now at University of Texas San Antonio, published a 2017 study documenting ARs that hit the southeastern U.S from 1979 to 2015.
If you are in the Southeast, make sure you have an umbrella as you go out for those Mother's Day lunches and dinners.