Two giant waves of water are rolling down from the country's far-northern middle expanse. One wave is following the path of the Missouri River toward the Mississippi River, carrying with it big chunks of ice. The second wave is taking a similar path down the Mississippi River from Minnesota. Both are the result of a long winter of heavy snowfall in Minnesota and the Dakotas followed by a short, sharp melt.

Both floods are more or less each one giant wave traveling at the speeds of their rivers, said Darone Jones, director of the Water Prediction Operations Division (WPOD) at the National Weather Service’s National Water Center (NWC) in Alabama.

The North Dakota wave traveled down the Missouri River to Nebraska and yesterday (March 18) reached northwestern Missouri. After passing Kansas City it will turn left, following the river, and make its way toward the joining of the Missouri and Mississippi rivers in St. Louis. [Top 10 Ways to Destroy Earth]

The Minnesota wave is taking the more straightforward route down the Mississippi River through Iowa, past St. Louis and into the ocean. Along the way, both waves should lose some water, so the downstream floods may not be as intense as those upstream.

Thanks to a strong storm system last week, the snow is melting very fast. That storm dumped heavy snow on Colorado and then turned into rain over North Dakota and Minnesota, Jones said. That rain was very cold, but still warm enough to trigger a sudden snowmelt. Ultimately, a couple inches of rainwater across a wide area combined with several inches of snowmelt to produce this intense flood wave.

And the chunks of ice in the flood make things worse, Jones said. Periodically, they clump up as the flood moves south, creating temporary ice dams. Those dams cause water to back up behind them, worsening the flooding before they break and release the wave again.

Posted by: Dana Mathewson at March 21, 2019 03:12 PM (rIYC+)

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