All of Louisiana at Risk for Excessive Rainfall Event Monday

There is an old joke whether you live in Boutte or Baton Rouge, Breaux Bridge or Bastrop if your driver's license says "Louisiana" then you live in a low-lying area. And while it's true that some parts of our state lie lower than others, it's also true that no matter where you live in Louisiana over the next couple of days heavy rainfall is going to be a concern for you. 

The Weather Prediction Center is the department of the National Weather Service that develops forecasts with a particular focus on precipitation. The WPC is the department that forecasts heavy snow storms, flash flooding, and in the case of Louisiana over the next several days, the threat of an excessive rainfall event.

An Excessive Rainfall Event is defined this way. When precipitation falls at a rate greater than drainage systems can handle, that's when you have an excessive rainfall event in the Lafayette, Louisiana area that is a rainfall rate of about two inches per hour for an hour or so. Some other municipal systems can handle more rain, some can't handle that much.

The reason for all the rain is a trough of low pressure that extends southward into the northwestern Gulf of Mexico. The counter-clockwise circulation around this weather system is pulling moisture from the Gulf of Mexico over Louisiana. It is also providing lift in the atmosphere which creates instability and that's when the showers and storms start to form.

Over the next several days mornings will find the greatest concentration of showers and storms along the coast. As the day progresses those showers will begin to move onshore or form over land with the daytime heating. General rainfall rates will be less than one-quarter of an inch but some areas could see torrential downpours in a short period of time, hence the "excessive rain advisory" that has been posted for the state.

Meanwhile, don't look for conditions or the forecast to change that much over the upcoming work week. Forecasters have listed rain chances well above average all the way through next Friday. Again the greatest threat of rain will be along the coast in the morning and onshore in the afternoon hours.