Chicago, IL

Weather Forecast Office

Spring Flood Outlook for Northeast Illinois and Northwest Indiana

Outlook Valid
Spring 2020

Last Updated
February 13, 2020

Based on current conditions, the risk of flooding is near average to above average. The greatest risk of flooding is in the Rock and Fox River basins.

The spring flood outlook is updated each February and March. Next scheduled updates Feb 27 and Mar 12.

Risk Factors for Spring Flooding

To determine the relative risk of spring flooding, numerous factors are considered including snow cover, soil moisture, and current river conditions. A significant snow cover with high water content can increase the chances of flooding once warmer weather melts the snow. Elevated soil moisture conditions reduce the amount of rainfall that is soaked up by the ground and increase the amount of water that then runs off into area streams. Above average river levels reduce the river rise required to reach flood stage, while below average river levels would require an increased amount of river rise to reach flood stage.

Spring Flood Outlook 2020

Winter 2019-2020 Review

Fall 2019 Review

Spring Flood Risk Factors

Here is a general overview of spring flood risk factors across northeast Illinois and northwest Indiana river basins.

Risk Factor	Current Condition	Effect on Flood Risk
Fall/Winter River Levels	Above to Much Above Average	Increase
Fall/Winter Soil Moisture	Above to Much Above Average	Increase
Winter Precipitation (Snow Cover)	Below Average	Decrease
Winter Temperatures (Frost Depth)	Above Average	Decrease
Spring Precipitation	Unknown	-
Spring Temperatures (Snow Melt)	Unknown	-

Valid February 12, 2020.

Current Snow Cover and Snow Water Equivalent

Modeled snow cover (below, left) across the area ranges from near 0 inches to near 8 inches, which contains 0 inches to 1 inch of water equivalent (below, right). The deepest snow cover was in far northern Illinois and southern Wisconsin. The majority of the area had snow water equivalent values of less than 1 inch.

Valid February 12, 2020. Click here for the latest midwest snow analysis information.

Current Soil Moisture and Frost Depth

Modeled soil moisture values across the area (below) range from slightly above average to much above average, with the highest values in far northern Illinois and south central Wisconsin. In far northwestern Indiana, soil moisture values range from the 90th to 95th percentile for mid February while widespread areas of values increase to the 99th percentile in Illinois and Wisconsin.

Frost depth ranged from 0 to 10 inches across area river basins, with most areas at 3-5 inches.

Valid February 12, 2020. Click here for the latest soil moisture information from the Climate Prediction Center.

Current River Conditions

River levels across the area (below) ranged from near average to above average. The highest river levels were in the Rock River basin in northern Illinois.

River ice spotters report generally ice-free conditions across area rivers. Cold temperatures in the near future may cause an increase in river ice cover. River ice may still cause ice jams this spring, but confidence is low as of this outlook.

Valid February 11, 2020. Click here for the latest streamflow conditions from the USGS.

Spring Weather Outlook

The long term (next couple months) outlook from the Climate Prediction Center indicates near equal changes of below average, near average, or above average temperatures and precipitation.

Although snow cover, soil moisture, and recent river levels can provide some indication of the relative risk of spring flooding, any weather system that produces heavy rainfall could cause flooding. Spring flood outlooks are not able to assess the risk of flooding due to heavy rainfall more than a week or so in advance.

Detailed Flood Outlook

Click here for the detailed Spring Flood Outlook which includes tables with probabilities of flooding along area rivers. Relative flood risk can also be viewed on the Advanced Hydrologic Prediction Service (AHPS) page for our area.

Temperature

Temperatures for Winter 2019-2020 (through January) averaged about 6.0F above the climatic average in northeast Illinois.

*Temperatures for the entire winter of 2019-2020, and the graphic, will be updated in March.

December January February Temperature Anomaly

Precipitation

Precipitation for Winter 2019-2020 through January averaged about 0.8 inches above the climatic average in northeast Illinois.

*Precipitation for the entire winter of 2019-2020, and the graphic, will be updated in March.

December January February Precipitation Anomaly

Snowfall

The first measurable snowfall (>0.1 inches) across northeast Illinois generally occurred in mid-October. The first measurable snow in northwest Indiana generally occurred in early November. As of February 12, 2020, the season-to-date snowfall ranged from 10 to 30 inches across the area, with the highest totals (over 20 inches) to the northwest. Observed snowfall ranges from much below the climatic average in northwest Indiana to slightly above average (100-125%) in some portions of western and northwestern Illinois.

Heavy river ice conditions in January caused ice jams leading to minor flood impacts in a few areas.

Temperature

Temperatures were generally below the climatic average across northeast Illinois and northwest Indiana during Fall 2019. Temperatures trended more toward below average values when moving from southeast to northwest. Almost all areas experienced temperatures about 1-2F below average.

Precipitation

Precipitation was generally above the climatic average across northeast Illinois and northwest Indiana during Fall 2019. Precipitation was heaviest to the northwest near the Illinois/Wisconsin/Iowa border. Portions of northwest Indiana experienced precipitation about 125-150% of average while north central and northwest Illinois experienced precipitation greater than 200% of average.