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Just when we thought Tropical Storm Isaac was going to dissipate peacefully into much-needed rain for the central United States, news broke on Thursday that a dam was failing and 50,000 people would be evacuated on the Louisiana-Mississippi border. It's a surprising bit of news after the extensive reporting that that the area's levees were holding strong. So strong, in fact, that Army engineers were considering breaching a levee intentionally just to drain the area behind it. "Dam failure expected on the Tangipahoa River near Percy Quin park," the National Weather Service tweeted on Thursday, while CNN called the possibility of the dam's breach a "coin toss."

A mandatory evacuation order has been issued along the Tangipahoa River and a flash-flood warning issued for Tangipahoa Parish and Pike County, in Mississippi. This storm isn't over yet.

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