Northeast Wisconsin Spring Flood Outlook

Flood Outlook

The risk of spring flooding is below average for much of northeast Wisconsin including the following river basins: Fox, Little Wolf, Menominee, Oconto, Waupaca, Wisconsin, Wolf and Yellow. The greatest risk of spring flooding is along the Wolf, Wisconsin and Yellow River, where minor low-land flooding may occur. The increased flows on the Wisconsin, Wolf and Yellow River will be due to melting of the remaining snowpack and recent rainfall. The greatest potential for flooding will occur with any additional heavy rainfall events that occur on top of frozen soil in addition to continued snowmelt across the Northwoods. Central, east-central and far northeast Wisconsin has lost all snowpack, which will help to limit overall flood threat in those locations.

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 is 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. The greatest impacts occur near the mouth of the East, Fox, Oconto and Menominee River.

Seasonal Flood Probability Graphics

Seasonal Flood Probability Table

Current River Levels and Short Term Forecast River Levels

Flood Risk Factors

SnowPack

Snow cover and snow water equivalent has decreased significantly across all of northeast Wisconsin. Most notably, in areas from near Wausau to Shawano to Marinette and points south of that line, where there is no remaining snowpack. The Northwoods still maintains around 6 to 10 inches of snow depth, which is about 5 to 10 inches below normal for this time of year. Snow water equivalents in that area are around 1 to 4 inches, which is in the lowest 10th percentile for this time of year. The snow water equivalent for early to mid February in 2020, was around 4 to 8 inches, which was significantly greater than this year.

StreamFlow

Seasonal streamflows remain near to slightly above average this year, mainly due to the well above normal precipitation that occurred in 2019 into early 2020. There has been improvement in the streamflow over the past month, with nearly all sections of northeast Wisconsin approaching normal levels. The exception is across far northeast and east-central Wisconsin, where rivers are still running close to the 90th percentile.  This basically means that most of the rivers have some capacity to take runoff from typical rainfall events and any lingering snowpack.

Soil Moisture

Soil moisture is much lower for the Spring of 2021 versus the very saturated soils that existed in 2020.  In fact, much of northeast Wisconsin is running near to below normal for soil moisture, which has led to the area being labeled as "Abnormally Dry" in the latest drought outlook. This will allow the soils to absorb more melting snow and Spring rains, which would provide for only minor flooding at a few locations, pending any late season snow storms or significant rainfall events.

Snow Water Equivalent	Streamflow Compared to Normal	Soil Moisture Percentile

Looking Ahead

The above normal temperatures over the past couple weeks along with colder nights has allowed the snow to melt off at a more gradual pace.  Any additional snowpack across the north will likely have limited impact as the depth and snow water equivalents remain below normal.  The main flooding threat appears to hinge on any heavy rainfall events or late season snow storms that impact the area. Of course, any heavy rain that fall before all of the frost is out of the ground, will lead to increased runoff as well; however, conditions have improved across much of northeast Wisconsin. The outlook for March and the spring season shows increased chances for above average precipitation.

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, GRB)
• 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

This is the final Spring Flood Outlook for this season.

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

National Weather Service-Green Bay

nws.greenbay@noaa.gov