Southern Wisconsin Spring Flood Outlook -Updated March 11

Flood Outlook as of 3/11

The risk of spring flooding is average for southern Wisconsin including the following river basins: Baraboo, Wisconsin, Sugar, Pecatonica, Rock, lower Fox, upper Fox, Sheboygan, Milwaukee, and Root. 

River flooding in Wisconsin typically occurs in March and April when there is a rapid snowmelt and/or heavy rain. But, it can happen any time of year when there is heavy rain.

Shoreline flooding and river flooding near river mouths near Lake Michigan, due to the High Lake Michigan Water Levels in expected to continue into the summer. Impacts mainly occur due to strong storms with high winds and waves. Lake level will largely depend on the amount of precipitation.

Seasonal Flood Probability Graphics 

Seasonal Flood Probability Table 

Current River Levels and Short Term Forecast River Levels

Flood Risk Factors

Current Conditions

Most of the snow pack has evaporated and melted. There was a very deep snowpack with a high water content and that moisture is still working its through the soils, subsoils, and making its way to the rivers. The Wisconsin River will be elevated into next week as a result of melting snow and rain from the northern and central portions of the basin.

Rivers and streams are rising from the melting snow. Streamflows are average to above average. 

Soil moisture is average, but is slightly saturated from the recently melted snow. The slow melting of the snow is not overly saturating the soils.

Frost depth is shallow and has completely thawed in some areas. It ranges from 0 to 10 inches, and 1 to 5 inches has thawed at the surface. This will allow for some any future rainfall to absorb into the ground.

Snow Water Equivalent	Streamflow Compared to Normal	Soil Moisture Percentile

Flood Risk Factors as of 2/26

SnowPack

The water contained in the snowpack is above average. Most of this snow will make its way into rivers when it melts, increasing the flood risk. Snow water equivalent values are 2 to 4 inches, with the highest amounts in far southern and far southeast Wisconsin. A few areas have over 4 inches. With ongoing melting and evaporation these values are going down, but they remain high. The water content is in the 60 to 90th percentile for this time of year.

There is less snow than normal in the upper Wisconsin River basin resulting in the average risk of spring flooding in the lower Wisconsin River.

StreamFlow

Streamflows have been much above average due to a very wet 2019 and they remained elevated going into this winter due to average precipitation in 2020. Levels went down somewhat over the past several weeks with all the recent precipitation in the form of snow. With the mild temperatures causing melting they have started to rise somewhat. Currently streamflows are close to normal across southern Wisconsin, except for the upper Fox basin, which is above normal, and the lower Wisconsin and Milwaukee River basins, which are below normal. Normal streamflows combined with the deep snowpack adds to the flood risk. Rivers will be able to hold some of the melted snow and any additional rain, but not as much than if they were lower.

Soil Moisture

Soil moisture is somewhat elevated, in the 70th to 80th percentile. There is some room in the soil to absorb moisture, but it could be better. Frost depth is 4-10 inches, which is shallow to moderate. A shallow frost will thaw sooner and allow the ground to soak up moisture, helping to limit flooding. But, there is a lot of water to absorb with the deep snow pack.

Looking Ahead

Precipitation from Wednesday and early next week could result in some minor flooding. Beyond that flooding will depend on whether there is moderate to heavy rain. 

7 Day Precipitation Forecast

Extended outlooks from the Climate Prediction Center:

8 to 14 Day Temperature Outlook	8 to 14 Day Precipitation Outlook
March Temperature Outlook	March Precipitation Outlook

How To Prepare Safety

Preparedness/Early Actions:

• Get a NOAA Weather Radio to be alerted to flash flood warnings and river flood warnings
• Monitor weather forecasts for heavy rain potential
• Have a communications plan for your family and a place to meet in higher ground.
• Monitor river levels and forecasted river levels online: (National Site, USGS, MKX)
• Know a safe way to exit your home and neighborhood, including any roads susceptible to flooding
• Prepare your home:
  • Consider flood insurance, especially if you are in a flood prone area - (may require 30 day notice)
  • Make sure your sump pump is working and consider a backup.
  • Have a professional install check-values to prevent floodwaters from backing up into the drains of your home
  • Keep important documents in a waterproof, elevated container, not in the basement.
  • Remove snow from roof, downspout area, and away from base of home
  • Finish any outdoor projects that may be affected by heavy rain or flood waters
• Prepare (Flood Ready, Flood Safety) 

How To Stay Safe During a Flood:

• Heed evacuation orders and evacuate your home if it is at risk
• Turn Around, Don't Drown - never drive through flooded roads
  • You do not know how deep the water is or if the road has been washed out
  • You may damage your vehicle
  • You put yourself and first responders at risk

Additional Information

March 11, 2021 Webinar Recording and Slides

Feb. 26, 2021 Webinar Recording and Slides  

Feb. 12, 2021 Webinar Recording

If you have any questions or comments about this spring flood outlook please contact:

Sarah Marquardt

Senior Service Hydrologist

National Weather Service Milwaukee

sarah.marquardt@noaa.gov

For a quicker response during non business hours please contact nws.milwaukee@noaa.gov.