Dry Weather Across the Eastern Corn Belt

If you look at the Corn Belt this spring you see two different stories. Much of the western Corn Belt has enjoyed above normal rainfall if you look at the last 30 and 90 days (first two maps below). However, below normal rainfall was common across much of Illinois, and parts of Indiana, Ohio, Kentucky and southeastern MO. Those areas have widespread rainfall departures of 2 to 4 inches in the last 90 days.  A few isolated spots scattered across Illinois have departures of 4 to 6 inches.  A particularly dry spot in southeastern Illinois, southwestern Indiana, and western Kentucky has rainfall departures of 6 to 8 inches at 90 days.

This has definitely had an effect on streamflows (third map) and soil moisture (fourth map). Keep in mind that while the streamflows are low for this time of year, it is relative to the normally high streamflow in spring. The same would be true of soil moisture.

The last map shows the U.S. Drought Monitor depiction for Illinois as of April 17 with a large swath of “abnormally dry” conditions across central and southeastern Illinois.

There are some opportunities for rainfall between now and Saturday but the expected amounts are modest at 0.5 to 1.0 inches total. In the past few weeks, the forecasts have been overly optimistic about rainfall amounts. This is likely the result of the soils drying out, cutting off the local source of atmospheric moisture (humidity).

The 90-day precipitation departure for the Midwest, ending on April 24, 2012. Click to enlarge.
The 30-day precipitation departure for the Midwest, ending on April 24, 2012. Click to enlarge.
The 7-day average streamflow showing areas with very low flows for this time of year, USGS. The areas in the lightest tan are in the 10-24 percentile class and classified as "below normal" by USGS. The next shade darker is at the 6-9 percentile class, and is classified as "moderate hydrologic drought". The darker shade of brown is at the less than 5 percentile class and is classified as "severe hydrologic drought". Click to enlarge. Link to original (updated daily).
University of Washington's soil moisture model run for April 23, 2012. Click to enlarge. Link to original (updated daily).
Here is what the U.S. Drought Monitor says for Illinois. Click to enlarge. Link to original (updated weekly).
Advertisements