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Average to Above Average Spring Flood Risk

Key Points

  • Above average risk for flooding in south-central Wisconsin
  • Average risk of flooding for southeast Wisconsin
  • Impactful flooding is still possible; where flooding occurs and how bad it will be depends on where there is heavy rain
  • The ground is very saturated, which will cause increased runoff and flooding potential.
  • Above average risk of flooding and backwater effects of river mouths near Lake Michigan due to high lake levels

Link to Spring Flood Outlook Flyer

What's Has Changed in mid March?

Things have improved somewhat, now that the snow has mostly melted, but flooding is still possible. Mild temperatures and below average precipitation in the past three weeks allowed snow to slowly melt and evaporate. This was perfect timing because river levels lowered somewhat with the dry weather and they had room to accommodate the melting snow. Now they are back to high levels for this time of year.  

Risk of flooding has decreased somewhat. The risk of exceeding moderate and major flood stages has decreased to about average risk level. In south-central Wisconsin there is still an elevated risk of exceeding minor flood stage this spring. In southeast Wisconsin the risk of exceeding minor flood stage is down to average. In the Wisconsin River basin there is still an above average risk of flooding but there is still a deep snowpack in the northern part of the basin.

Potential Impacts

The ground is unable to accept much additional water, so increased runoff is expected, which will increase flooding potential. In addition, runoff into rivers that are already high further increases potential for river flooding. Minor flooding is expected, however more impactful flooding is possible, especially with any heavy rain.  Flood risk could remain somewhat elevated into summer if soils remain saturated.

River flooding and inundation of river mouths near Lake Michigan, due to the high Lake Michigan water levels, is expected to continue into the summer.

Note: River flooding in Wisconsin typically occurs in March and April when we have a rapid snowmelt and/or heavy rain. But, it can happen any time of year when we get heavy rain.

 

Current Conditions

 

Winter Conditions Summary

Precipitation was close to average for the winter season. Soil moisture remains historically high around the 99th percentile. It was the 6th warmest winter on record in Milwaukee and 14th warmest in Madison.

Mild temperatures this winter have minimized the amount of ice and ice thickness in the rivers. As a result, the risk of spring break up jams is low. Break up jams cannot be predicted and are still possible when warmer temperatures cause ice to break up and move down the river. It can jam up at river bends or bridges causing flooding.

 

Forecast/Outlook

Mid to late March is looking wet. Extended outlooks from the Climate Prediction Center.

 

Previous Maps

 

Typical Spring Flood Risk Factors Include:

(Red if already going to factor into 2020 Spring Season)

  • High river levels
  • High soil moisture
  • Normal to above normal winter precipitation
  • Average frost depth - Not a threat anymore
  • Rapid Snow Melt -Not a threat anymore
  • Heavy rain
 

 

 

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
  • Monitor river levels and forecasted river levels online: (National Site, USGS, MKX)
  • Consider flood insurance, especially if you are in a flood prone area - (may require 30 day notice)
  • Prepare (Flood Ready, Flood Safety
  • 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.
  • Have a communications plan for your family and a place to meet in higher ground.
  • Finish any outdoor projects that may be affected by heavy rain or flood waters

Contact information:

Sarah Marquardt

NWS Milwaukee/Sullivan Service Hydrologist

Sarah.Marquardt@noaa.gov