Snowfall across the central US has been slightly below average so far this winter and stands in stark contrast to last winter. However, the impact on soil moisture, rivers, and streams has been minimal.
Here is an example of snowfall differences. At Chicago O’Hare airport the snowfall total for this winter through January 14 is 13.7 inches. Last year through this date it was 35.0 inches and the 1981-2010 average is 14.2 inches.
In the first map are the snowfall departures for this winter. All the areas in tan or beige are up to 10 inches below average. That includes almost all of Illinois, Minnesota, Iowa, Missouri, Indiana, and Kentucky, as well as large portions of the Dakotas, Nebraska, Kansas, Wisconsin, Michigan, and Ohio. Areas in green are above average and include a small area in far southern Illinois and another around Moline. Snowfall is above average across upper Wisconsin and the Michigan UP.
The second map shows the snowfall departure map for the same period last winter. At that time, large parts of the central US were up to 20 inches above average on snowfall. There was an area of below-average snowfall that stretched from eastern Colorado to parts of Iowa and Minnesota.
However, low snowfall in the central US does not always mean that we are dry. In many cases, the lack of snowfall can be is made up by more rain. Here is the map of precipitation (rain plus the water content of snow) departures for the last four and a half months. That is the same period as shown in the snowfall maps. An area of above-average precipitation stretches across eastern Nebraska and Kansas, and into Iowa, Missouri, central Illinois, central Indiana. There areas of below-average precipitation in far southern and northern Illinois, as well as Minnesota, the Dakotas, southern Wisconsin, and Ohio.
Usually, I do not worry too much about dry weather during the colder months of the year because the corn and soybeans are out, and everything else is dormant. As a result, demand on soil moisture, rivers and streams, and lakes is very low. Right now the USGS is reporting that stream flows across Illinois and the central US are within the normal range. USDA reports of topsoil and subsoil moisture in Illinois are 92 and 90 percent respectively in the adequate to surplus categories.
