February 22nd, 2007 05:17 EST
Winter Releases Its Icy Grip On The Nation's Midsection
As winter releases its icy grip on the nation's midsection, NOAA weather forecasters and hydrologists now contend with the possibility of significant flooding from rapid snow melt. Flooding and flash flooding are occurring now in several states from the plains of southeastern Colorado to central Indiana. A strong spring storm system moving east from the Pacific is expected to make conditions worse over the coming weekend.
"Considerable snow pack developed over much of the central part of the country since late December," said Mike Looney, chief of Services Division at the NOAA National Weather Service Central Region Headquarters in Kansas City, Mo. "Warmer temperatures over the past few days have really increased the rate of melting snow. The presence of saturated soils in many areas is compounded by the fact that the soil is frozen a few inches below the surface. Since frozen soil can't absorb the moisture, it's all turning to runoff."
"Some low-lying and poorly-drained areas already are experiencing flooding, and there have been a number of local and county roads closed by high water in several states. As temperatures get warmer, the snow, holding 1-3 inches of water, melts that much faster, so it won't take much rain to cause really significant flooding," added Looney.
A major winter storm is expected to develop over the northern and central Rockies on Friday, moving across the Central Plains through the weekend. The weekend forecast calls for showers and thunderstorms over northeast Kansas and northwest Missouri into the Mississippi and Ohio River valleys as moisture from the Gulf of Mexico collides with the cold air wrapping around the winter storm. The warm side of the winter storm will produce rain. Heavy rain and possible severe weather may occur across central Nebraska and much of Kansas on Friday, spreading east through the weekend. On the cold side of the winter storm, blizzard conditions are possible across parts of northeast Kansas, northwest Missouri into eastern Nebraska and western Iowa.
The NOAA National Weather Service has two Web sites that provide flood statements and warning information as well as graphical depictions of current conditions on stream beds. The NOAA Hydrologic Information Center's map of forecast offices at provides information on current conditions for individual drainage areas across the country. Current river stage and forecast information is available on the NOAA Advanced Hydrologic Prediction Service national map. The latest information regarding the threat of severe weather is available from the NOAA Storm Prediction Center.
NOAA National Weather Service Central Region forecast offices with flash flood or flood statements and warnings in effect include Riverton, Wyo.; Pueblo, Colo.; Dodge City, Kan.; Kansas City, Mo.; St. Louis, Mo.; Central Illinois at Lincoln; Northern Indiana at Syracuse; and Indianapolis. High water has already forced closure of many rural roads in low lying areas of those states.
NOAA's current Significant River Flood Outlook issued Feb. 20 locates the highest possibility of significant river flooding in eastern Iowa, northeast Missouri, southeast Minnesota, southern Wisconsin, the northwestern three-fourths of Illinois and extreme northwest Indiana.
Looney said runoff from the melting snow has raised the level of some mainstream rivers above flood stage, but that flooding is worse on many smaller tributaries becoming overwhelmed by the volume of water.
"We encourage everyone to use caution in low-lying areas this weekend," Looney said, "especially in areas that get any rain at all. We caution all motorists to avoid driving into flood waters no matter how well they know an area. Flood waters can undermine roads, washing them away with no sign of the damage done. Quiet little streams already are becoming raging torrents, and those conditions only are going to get worse as temperatures rise and rain moves in."
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