A consistent atmospheric pattern is behind some of the Gulf Coast's most significant heavy rain events in May and June, according to an analysis by the Storm Station.

The team of meteorologists at WBRZ reviewed every May and June since 2003, when the National Oceanic and Atmospheric Administration (NOAA) began archiving daily weather maps. The top three-day rainfall totals at Metro Airport in Baton Rouge were compared to surface and upper-level maps to identify key weather features during each event. The top eight events all shared a similar setup: a stationary (or slow-moving) front stalled along the Gulf Coast and/or an upper-level trough positioned to the west.

A stationary front is a boundary between two different air masses that has lost its momentum and stopped moving. Because it is stalled, storms that form along it repeatedly track over the same areas.

An upper-level trough is an area of low pressure in the atmosphere, typically between 18,000 and 30,000 feet overhead. Troughs to the west act like atmospheric vacuums, pulling moist, tropical air upward from the surface and providing continuous lift to create stormy weather.

Here is how that dual setup played out across the top eight events:

These patterns often occur during May and June because of a seasonal shift in global wind currents. The jet stream, which pushes weather systems across the country, weakens and migrates northward toward Canada during late spring.

As the jet stream moves north, steering currents over the southern United States slow down. Cold fronts that easily sweep through Louisiana in January, February, and March lose their forward momentum and stall right over the Gulf Coast states for days at a time. A stalled front in May or June causes significantly more flooding than one in winter for two reasons.

First, humidity starts surging northward during these months as the seasonal warming process begins in the Gulf. Winter air masses typically struggle to have a lot of moisture.

Second, the combination of a stalled front and a slow-moving upper-level trough creates a prolonged triggering mechanism. The upper trough continuously pumps energy over the stalled front, forcing moisture-rich air to lift and condense into storms. Because steering winds are practically nonexistent, storms repeatedly pass over the same areas in a process known as training, dropping relentless rain over the same streets and bayous for hours or even days.

While severe weather draws significant attention in the spring and tropical systems steal the show in late summer, seemingly boring weather features in the transition period can be just as impactful. Recognizing this recurring pattern allows the Storm Station to predict weather events that can lead to heavy rain and flooding.

For the upcoming days (June 15-18, 2026), a stalled front will be parked between I-20 and I-10 in Louisiana and Mississippi. Not only will a broad upper-level trough be positioned across the central United States, but a tropical disturbance over Mexico and Texas may serve as an additional upper-level trough to complete the pattern identified as a heavy rain setup. 

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