March 16, 2019

Historic Storm Triggers Historic Flooding Across Nebraska

The record-setting storm that blew across the Plains states earlier this week led to a catastrophic flooding situation in Nebraska, unleashing the some of the worst flooding ever seen by many of the region's living residents Waterways across eastern Nebraska surged over their banks as a confluence of weather conditions led to a sudden surge of runoff into rivers and streams.

An intense low-pressure system developed over eastern Colorado and western Kansas earlier this week. The storm set record minimum air pressure readings in many communities across the region; storms of this strength usually don't form this far south or west. The storm brought blizzard conditions to Colorado, Nebraska, and the Dakotas—the Colorado Springs airport recorded a record-high 97 MPH wind gust—and a round of severe thunderstorms on the southern end of the system.

The eastern edge of the system didn't get much attention beyond the risk for severe thunderstorms. Strong winds circulating around the east side of the low brought in a surge of warmer temperatures from the south. Temperatures soared into the 60s through parts of Nebraska and Iowa, a sudden change after so many weeks of subfreezing temperatures. The situation led to an intense period of flooding across the regions rivers and streams.

Sen. Ben Sasse has been tweeting out pictures of the flooding and damage as he tours the flooding in his home state today. The images of the flooding are otherworldly in many places.

NWS Omaha, located in Valley, Nebraska, had to evacuate their office and relocate 155 miles away in Hastings, Nebraska, due to the rising waters. A helicopter tour later that day revealed that their office was completely surrounded by floodwaters.

Multiple communities, including Fremont, were completely isolated by the flooding due to high waters and severed bridges. Large chunks of ice flowing through floodwaters damaged and destroyed homes, businesses, and bridges.

Dozens of river gauges across Nebraska—as well as surrounding states—saw water levels reach major flood stage. The Missouri River in Omaha is expected to crest at 34.5 feet on Sunday, firmly within moderate flood stage and six feet below the all-time record of 40.2 feet.

A significant number of waterways reached their highest crests ever recorded. We saw a record crest along the Elkhorn River, not far from Norfolk, Nebraska...

...and a record crest along the Platte River near Ashland, Nebraska...

...and along the Platte River near Leshara, Nebraska...

...and along the Platte River at Louisville, Nebraska...

...and along the Big Sioux River near Hawarden, Iowa...

...and along the Big Blue River near Crete, Nebraska...

...and on, and on.

No single factor led to the flooding; each factor compounded on the next to created the perfect conditions for historic flooding.

The ground was still frozen from many weeks of subfreezing temperatures, which means that much of the rain that fell and snow that melted this week simply ran off into waterways.

The above chart shows temperature data for Omaha, Nebraska, from March 1 through March 16. Omaha spent most of March below freezing before this week's storm. The storm sent temperatures surging up to 60°F on March 13, accompanied by 1.37" of rain over the course of three days.

Daily snow depth measurements between March 8 and March 16, 2019. (NOAA/NOHSRC)

The sudden burst of warmth combined with the steady, heavy rainfall chewed away at the snowpack left on the ground from previous snowstorms. Omaha went from 7" of snow on March 8 to no snow on the ground by March 13.

Frozen ground combined with a sudden snowmelt due to warm temperatures and heavy rain all forced massive amounts of excess water into local rivers and streams. This sudden surge of water sent rivers to record crests.

This was a relatively well forecast event. It didn't come as a surprise as far as forecasts go. The National Weather Service warned of "major to historic flooding possible" across the region. I mentioned the threat in my post on the storm earlier this week. But when you're experiencing record crests, you have no frame of reference for what to expect because you've never experienced it before.

Excess water in Nebraska and Iowa will slowly filter downstream through next week. The National Weather Service expects major flooding along the Missouri River near St. Joseph, Missouri, by next Thursday. Water levels in the hardest-hit areas of Nebraska should slowly recede through next week. A threat for rain on Tuesday could lead to around half an inch of rainfall for the affected areas. Waters should recede enough that the forecast rainfall shouldn't add insult to injury.

[Top Image: March 16, 2019 (RAMMB/CIRA)]

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I graduated from the University of South Alabama in 2014 with a degree in political science and a minor in meteorology. I contribute to The Weather Network as a digital writer, and I've written for Forbes, the Washington Post's Capital Weather Gang, Popular Science, Mental Floss, and Gawker's The Vane. My latest book, The Skies Above, is now available. My first book, The Extreme Weather Survival Manual, arrived in October 2015.