January 8, 2010

Be Aware Of Possible Spring Flooding Due to Extreme Cold, Snowpack

With December 2009 being one of the coldest on record, lakes, rivers, and streams are accumulating significant ice mass, putting the state in danger of spring flooding if there were to be a quick warm-up.

Nebraskans should be aware that if there isn’t a slow, prolonged thaw, snow will melt too quickly and the runoff will likely contribute to ice jams and flooding.

Farm fields near tributaries could see some flooding as there should be little infiltration from snow into the soil profiles as surfaces are currently at or below freezing across much of eastern Nebraska.

Current snowpack in eastern Nebraska is storing about 1.5-2.5 inches of water, not including moisture from the Jan. 6 event. Thus, flooding could be similar, or worse than the flooding seen in the early 1990s. Although it is too early to tell, people should be aware of the potential.

A slow warm-up this spring will minimize impacts and make room for incoming water. Current weather models do not point to any imminent large scale warming before the end of January. In fact, the potential exists for another strong winter storm around the third week of January. If this verifies, the flood potential will increase above current concerns.

The current snowpack is knocking 15 to 20 degrees off daily temperatures. Still, the state doesn’t want to see a sharp warm-up, and February often can have warm periods.

Ice jams also may become a problem depending how quickly snow pack melts, releasing water and breaking up ice.

Al Dutcher
State Climatologist