June 15, 2013 Isolated Severe Thunderstorm in Jefferson County

Quick Facts:

What Severe Storm with 1" diameter hail and gusty winds to 50 to 60 mph

935-950 pm CDT    June 15, 2013

Where Lake Mills area east to Johnson Creek area
Impact Trees knocked over, branches broken, lawn furniture blown around. Brief heavy rains on order of 1 to 1.5 inches with ponding of water.

An isolated severe thunderstorm pulsed up over northwestern Jefferson County in the Lake Mills area and proceeded to move east to the Johnson Creek area.  It produced hailstones up to 1 inch in diameter just west of Lake Mills.  Additionally, it generated strong gusty winds which knocked over a 1-foot diameter tree as well as sheared off other small trees and knocked other large tree branches down. After the storm affected Johnson Creek it weakened once it moved through Waukesha County.


David Strom, resident of Johnson Creek, filed this report:  Tree debris and lawn furniture were blown in different directions, which is typical of a wet microburst.  Much of the tree damage was confined to a 1-block wide path from along and just south of I-94 from one mile west of Lake Mills to the Johnson Creek water tower.  The strongest winds lasted a minute or so and there was a "wind roar."  Some residents headed to their basement.


Below are some pictures David took.  Click on images for a larger version.

Johnson Creek Pic 1  Johnson Creek Pic 2

Below is a radar animation showing the movement of the severe storm through the Lake Mills to Johnson Creek area.  On the left is reflectivity with the reds indicating heavy rain and possibly hail. On the right is base velocity indicating the speed of the winds relative to the ground. Green colors are related to targets approaching the radar site and red colors are related to targets moving away from the radar site.  The radar site is represented by the green circle in the lower right of each image.  The brighter green colors indicate stronger winds.  Note how the wind speeds increase as the thunderstorm approaches Johnson Creek.  Click on animation for a larger version.

June 15 2013 rdar animation 


Kapela/ET, WFO Milwaukee


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