The Washington Post

Lack of winter snow reduces spring flood threat

The risk of flooding this spring is below normal over large parts of the country (NOAA)

“We’re not forecasting a repeat of recent historic and prolonged flooding in the central and northern U.S., and that is a relief,” said Laura Furgione, deputy director, NOAA’s National Weather Service. “The severity of any flooding this year will be driven by rainfall more so than the melting of the current snowpack.”

Snow cover extent in the Lower 48 this past winter was 3rd lowest in the 46-year record developed by Rutgers University Global Snow Lab.

Last year, a combination of a significant spring snowpack and heavy rains resulted in historic flooding of the Mississippi as well as Missouri and Souris rivers, events classified as billion dollar weather disasters.

But this year, in the upper Mississippi and Upper Missouri Valley, NOAA says the flood risk is below normal:

precipitation .... has been less than 50% of the normal across the Upper Mississippi and Upper Missouri Valleys. Snowpack in these regions is well below levels needed to warrant large scale flooding, and will not play a role in this year’s spring flooding across the northern US. The High Plains of the Missouri Basin contain little to no snow...

Snow cover maps compiled from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA’s Terra satellite on March 3, 2011 (top) and March 5, 2012 (bottom).

In 2012, areas that are usually snow covered are bare, including parts of Montana, Wyoming and South Dakota. The Snake River Plain in southern Idaho is clearly visible. This low-lying valley is the track of the hotspot that is now under Yellowstone National Park. In the east, the Great Lakes area, southern Ontario and the East Coast of the United States have much less snow cover than they did at this time last year.

The small areas in the Lower Ohio Valley and central Gulf Coast where flood risk is above average has nothing to do with snowpack or lackthereof, but rather elevated soil moisture and/or high streamflow levels from recent rains.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.


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