The heavy rainfall across the Midwest in recent weeks has increased the risk of flooding on the Illinois and Mississippi Rivers. Rainfall totals were highest in western Illinois, northern Missouri, much of Iowa, southeastern Minnesota, and western Wisconsin, and ranged from 6 to 12 inches in the last 30 days. See the MRCC map below.
The National Weather Service produces forecasts of river levels based on current conditions and precipitation over the next 24 hours. At Quincy Lock and Dam, the Mighty Mississippi River is expected to be in “major” flood by sometime Thursday (first graph). See the latest forecast for this site here.
It is a similar story on the lower Illinois River. The current and forecasted river stage at Hardin, IL (second graph) shows that the river will reach “major” flood stage by next Monday. See the latest forecast for this site here. Of course, more rainfall in coming days will change these forecasts.
More rain fell over Illinois over the Memorial Day weekend. The heaviest amounts were in the central part of the state and ranged from 2 to 6 inches (yellow to dark red in the map below).
Right now the statewide average rainfall for May stands at 5.03 inches, based on preliminary data. More rain is forecasted for today and much of this week. So this total is likely to increase as we go through the week. By contrast, Illinois received only 2.5 inches in May 2012.
Tornado risk has been on a lot of minds after the events in Moore, OK. For the first time that I can recall, the local TV station (Champaign) ran an advertisement for pre-constructed storm shelters.
In 2011, we produced county-level tornado track maps for all counties in Illinois to measure the historical risk of tornadoes across the state. These maps were based on data from the NOAA Storm Prediction Center for the period of 1950 to 2010. For example, below is the map for Cook County that shows tornado tracks and touchdowns, color-coded by (E)F-scale.
To me, the strongest reminder that a strong tornado can pass through Chicago is the April 21, 1967, Oak Lawn F-4 event that killed 33 and injured 500. Here are some pictures of from the Oak Lawn Public Library of that event that look a lot like the damage in Moore, OK.
You can see the rest of the maps on the Tornado Maps page at the Illinois state climatologist website.
The latest US Drought Monitor map from May 14, 2013, shows a Dr. Jekyll/Mr. Hyde nation when it comes to drought. Much of the country to the west of the 96° longitude is in some stage of drought while the country to the east of that line is largely drought free for the moment. Hardest hit have been the Plains states which in some cases are in year 2 or 3 of this drought.
By the way, the US Drought Monitor began about 13 years ago to provide one, unified map of drought across the United States. It is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration with lots of input from scientists, state climatologists, state and local agencies, university extension, landowners, farmers, etc. Maps are updated weekly and released on Thursday mornings.
The precipitation pattern so far this year reflects these differences between east and west. The map is the current year to date departure from average precipitation produced by the NWS. Areas in green and blue are 2 to 8 inches above average and include much of the Midwest and Southeast. Areas in yellow are 2 to 6 inches below average. Hardest hit so far has been the West Coast with departures more than a foot below average. There are large areas shaded gray which show near-average conditions. However, much of the west needs many more months of average precipitation or even above-average precipitation to start a recovery from their current drought situation.
The National Climatic Data Center has a product that gives a rough idea of the amount of precipitation needed over the next 6 months to recover from drought. I say “a rough idea” because the timing and intensity of the precipitation is important as well. The effect of getting 3 inches in 30 minutes is different than getting 3 inches over 3 days. The first will cause lots of runoff while the second will have a better chance of recharging soil moisture. As you can see, it will take a considerable amount of precipitation in the Plains states to get out of their current situation.