CEDAR RAPIDS, Iowa (KCRG-TV9) - The National Weather Service issued its first spring flood outlook of the season. A variety of factors puts the risk of springtime flooding near or somewhat below the long-term odds. This is the case on the Mississippi River as well as the tributary rivers such as the Cedar, Iowa, Wapsi, and the others that are in eastern Iowa.
Soil Moisture
The moisture in the soil across most of eastern Iowa is near or below normal. In fact, a moderate drought exists in southeastern Iowa. In central and southern Minnesota, the ground is wetter than normal, which would affect mainly the Mississippi River. As the ground thaws, it’ll be able to absorb water fairly well.
Frost Depth
Frost is found as much as one to two feet deep in Iowa and southern Minnesota. This is because of the very cold temperatures that happened early in winter before there was much, if any, snowpack. Because the ground is frozen so deeply, water will run off into streams and rivers more than it otherwise would.
Streamflow
Streamflow is the amount of water moving through the river at a given place. Streamflow is near or somewhat above normal on the Mississippi and some tributary rivers. It’s below normal in southern Iowa in the moderate drought area. If the rivers were running high already, this would heighten the flooding risk; however, they are not far from what is typical and are able to contain more water.
Water in the Snowpack
Snowmelt over the past few days has led to much less snow on the ground locally. As a result, the amount of water that’s left in the snowpack is less than an inch, and in many cases is closing in on zero. Southern Minnesota has about one to four inches of water in the snowpack as of Thursday. However, the snowpack is running below normal, so this amount of water is not concerning.
These are all general factors and are a broad indication of the most likely scenario. A situation such as a small-scale heavy rain event, or a significant ice jam, are too localized to be able to predict far in advance and include in this type of outlook.
An updated outlook will be issued on March 1.