Chicago, IL

Weather Forecast Office

Spring Flood Outlook for Northeast Illinois and Northwest Indiana

Outlook Valid
Spring 2020

Last Updated
March 12, 2020

Based on current conditions, the risk of flooding is near average to above average. The greatest risk of flooding is in the Rock River basin. Conditions have improved slightly since previous outlooks.

The spring flood outlook is updated each February and March. Next scheduled update spring 2021.

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 March 12, 2020.

Current Snow Cover and Snow Water Equivalent

Modeled snow cover (below, left) across area river basins was 0 inches (below, left) and water equivalent was 0 inches (below, right) for all areas. All snow cover melted since the previous spring flood outlook update.

Valid March 11, 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 above average to much above average, with the highest values in far northern Illinois and southern Wisconsin. In far northwestern Indiana, soil moisture values range from the 90th to 95th percentile for early March while values increase to the 99th percentile in Illinois and Wisconsin.

Frost depth was near 0 inches across area river basins. Almost all remaining frozen soil had thawed since the previous spring flood outlook update.

Valid March 10, 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 much above average. The highest water levels are in the headwaters of the Rock and Fox River Basins.

River ice spotters report ice-free conditions across area rivers. The chance of ice jams is low for the remainder of spring.

Valid March 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 averaged about 4-5F above the climatic average for northeast Illinois and northwest Indiana river basins.

Precipitation

Precipitation for Winter 2019-2020 was near to above the climatic average for northeast Illinois and northwest Indiana river basins.

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.

Season-to-date snowfall (through late February)ranged from 15 to 35 inches across the area, with the highest totals (over 30 inches) to the northwest. Observed snowfall ranges from below the climatic average (50%) 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.