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Hurricane Isaac will produce a variety of inland flood impacts as it slowly moves northwest.

Isaac has already produced close to a foot of rain near the southeast Louisiana coast.  Keep in mind that when an inland-moving tropical system slows – inland flood pacts are certain.  Isaac has all the traits needed to provide a variety of inland hydrologic impacts, both along the coast and well inland.  Total rainfall amounts could near 24 inches in localized spots with widespread amounts around 12 inches.

Here is a summary of rainfall for the past 24-hours.

As is typical with inland-moving hurricanes, a variety of hydrologic impacts can be expected.

Widespread pooling of water – one of the more significant impacts, especially over the next few days, will be widespread pooling and ponding of water.  Due to the flat nature of southeast Louisiana and far South Mississippi, water will tend to pool and inundate many roads.  Smaller tributaries will merge with pooled water and inundate large areas.

Urban flooding – metro areas that receive 6 inches or more of rain will experience significant urban flood problems.  This includes New Orleans and Baton Rouge, as well as other urban centers along Interstate 10 across coastal Louisiana and Mississippi. 

Mainstem River Flooding – Significant flooding (causing inundation of secondary roads or flooding of structures) can be expected over a large portion of southeast Louisiana and southern sections of Mississippi for the rest of the week.

Here is the rainfall forecast for Isaac for the rest of the week and this weekend.




As the remains of Isaac move further northward late this week and this weekend, flood impacts will steadily decrease.  While scattered flood problems are still possible, especially urban and flood flooding, much of North Arkansas and Missouri have been dry and can handle significant amounts of rain.  In fact, for many portions of the Midwest, Isaac will bring drought relief.

Source: NOAA/NWS