A large swath of the country is at risk of moderate to major flooding this spring, from northeastern Montana through western Wisconsin following the Mississippi River south to St. Louis, National Weather Service flood experts are forecasting. Today the agency released an initial spring flood outlook for this high risk region and will release a national spring flood outlook on March 17.
For the third consecutive year, forecasters predict moderate to major flooding along the Red River of the North, which forms the state line between eastern North Dakota and northwest Minnesota and includes the Souris River Basin and the Devils Lake and Stump Lake drainages in North Dakota.
If the current forecast holds, the main stem Mississippi River is at risk for moderate to major flooding from its headwaters in St. Paul, Minn., all the way to St. Louis.
Areas of greatest flood concern are:
Devils Lake, N.D.
* Devils Lake at Minnewauken has about a 40 percent chance of exceeding 1,455 feet, which could partially inundate portions of the town of Minnewauken, including critical infrastructure and roads across the lake, emergency service routes and possibly a small section of the Amtrak train line.
Red River of the North in North Dakota and Minnesota
* Fargo, N.D., has about a 95 percent chance of exceeding major flood stage of 30 feet where portions of downtown Fargo begin flooding and temporary dike construction is necessary; and a greater than 20 percent chance of reaching or exceeding the 40.84-foot record set in 2009;
* Grand Forks, N.D., has a greater than 95 percent chance of exceeding major flood stage of 46 feet and near a 10 percent chance of exceeding the 54.35-foot record set in 1997.
James River and the Big Sioux River in South Dakota
* The James River at Huron, S.D., has about a 90 percent chance of exceeding major flood stage of 15 feet and a 30 percent chance of exceeding the record 21.28-foot level set in 1997;
* The Big Sioux River at Brookings, S.D., has a greater than 95 percent chance of exceeding major flood stage of 12 feet and nearly a 30 percent chance of exceeding the 14.77-foot record set in 1969.
Upper Mississippi River in Minnesota, Wisconsin, Iowa, Illinois and Missouri
* St. Paul, Minn., has about a 95 percent chance of exceeding major flood stage of 17 feet where secondary flood walls are deployed to protect St. Paul airport; and a 15 percent chance of exceeding the record 26.4 feet set in 1965.
NOAA’s flood forecasters point to several reasons for the anticipated floods. The ground in much of the north-central United States is frozen, water-saturated, and snow-covered. Forecasts for much of the region continue to call for persistent below-normal temperatures and above-normal precipitation for February, with an expectation for the snow pack to grow. In March and April, as temperatures rise and the snow melts, frozen ground and saturated soil will enhance runoff, causing streams and rivers to swell. The timing and the rate of snow melt and any rain that falls during snow melt contribute to the magnitude and extent of flooding.
“Excessive precipitation, mainly in the form of snow, coupled with continuously frigid temperatures has yielded a thick snowpack in much of the upper Midwest. We expect significant flooding when this snow begins to melt,” said Lynn Maximuk, central region director of the National Weather Service. “We urge residents in risk areas to closely monitor NOAA’s river forecasts and warnings, and prepare now for flooding.”
NOAA forecasters gauge flood risk by examining the impacts of precipitation, groundwater conditions, stream flow, snow conditions and weather forecasts. Computer models assist the forecaster by using these variables to calculate the probability that a certain river or lake will exceed its flood level (available online at http://water.weather.gov).
The source article Another Spring of Major Flooding Likely in North Central U.S. was published February 18, 2011 by NOAA .