Severe Weather Threat Monday in Louisiana – Repeat of Last Time?

Hellish nightmares of high water incidents are fresh in the minds of the folks in Lafayette, Duson, New Iberia, Youngsville, and countless other south Louisiana communities. It was less than a week ago these areas got more than a few months worth of rain in less than a few hours. Some of the stories of high water and high water rescues are certainly harrowing.

Last week's deluge scenario was set up like this. To the south of Louisiana was abundant moisture left over from former Major Hurricane Rafael. This moisture was streaming northward into Louisiana and interacted with an approaching cold front. This was all the catalyst needed to create those prodigious rainfall amounts.

The setup for this week, stop me if you've heard this, a dissipating tropical system, Tropical Storm Sara, is spinning off a lot of tropical moisture into the Gulf of Mexico. A strong cold front is pushing toward Louisiana from the west. Once again it looks as if the meeting point for these two atmospheric entities could have a Louisiana zip code.

There are two threats you will want to be aware of as we begin the work and school week. The first threat is the severe storm threat. The Storm Prediction Center has placed the entire state of Louisiana in the marginal risk zone for severe storms. Just remember a storm doesn't have to be designated as "severe" to cause significant damage to property and a risk to your health as well.

The second threat is the one that many Acadiana residents experienced last week. It's an excessive rainfall event. That happens when rainfall rates are higher than the ability of an area to drain away floodwater. In Lafayette's case that was a cloudburst of six to seven inches of rain in less than three hours. That's why so many roadways became impassable and school schedules had to be adjusted.

The graphic above from the National Weather Service Forecast Office in Lake Charles suggests that the higher rainfall totals, at least over a short period of time, will occur in southeastern Louisiana. But you'll note the shaded area does include the city of Lafayette and much of the eastern sections of Acadiana.

You can see that reflected in the graphic from Breyanna Lewis at KATC.com. Breyanna's depiction of the Euro Rainfall Model suggests that Lafayette could see an inch or better in showers and storms on Monday into early Tuesday. But Morgan City, Houma, and New Orleans seem to be in store for significantly more.

The timing for the heavy rain and storms across South Louisiana suggests that the afternoon hours are when the rain will begin but the heaviest rainfall will likely arrive and pass through Monday night and early Tuesday. There might be a lingering threat of a shower early Tuesday but skies should clear and temperatures will begin to cool down following the frontal passage.

Much of the work week after Monday's storms should be sunny, cool, and very fall-like. And if you're preplanning for Thanksgiving travel next week, unfortunately, it looks as if Wednesday, getaway day, will include a threat of showers and possible storms along the I-10 corridor. But, Thanksgiving Day should be much quieter.