During the late afternoon hours of Wednesday, June 2, 2010, a thunderstorm with large hail developed over east-central Dane County in the area between Deerfield and Marshall. It intensified as it moved southeast through northwestern Jefferson County through the Lake Mills area where it ultimately dumped hail stones on the order of 1 to 2 inches in diameter between 425 pm and 435 pm. It then weakened as it moved through the area between the cities of Jefferson and Ft. Atkinson.
In the Deerfield area this storm produced hail stones on the order of 3/4 inch in diameter. Below is a picture of these hail stones taken by Matthew Lazzara. Note that smaller hail stones were brought together in the thunderstorm cloud and coated with a larger, outer layer of ice.
Severe weather spotters - please continue to pass on to the National Weather Service any reports of hail stones with diameters of 3/4 to 7/8 inch. We still need these reports for entry into our monthly publication entitled Storm Data. Yes, we've raised the hail size criteria for severe thunderstorm warnings to 1 inch in diameter. It used to be 3/4 inch prior to 2009. In order to maintain the integrity of the Storm Data database, we still need to enter hail stone reports of 3/4 inch and 7/8 inch. The other criteria for severe thunderstorm warning issuance is maximum wind gusts of 58 mph or higher - unchanged from previous years.
If your vehicle or house sustained any hail damage from the June 2nd hail storm, please e-mail that information to firstname.lastname@example.org
Below are three radar reflectivity images showing the progress of the thunderstorm that produced large hail on June 2, 2010.....
Scattered locations in southern Wisconsin picked up 1 to over 2 inches of rains as the several rounds of storms passed through. The axis of the greatest rain amounts stretched across northern Dane Conty southeast through Jefferson County and then east near and just south of Interstate 94 to the Milwaukee area.
Below are two images showing where most of the rain fell. The image on the left is a raw plot of rainfall amounts. Note that the 24-hour rainfall total at the Milwaukee/Sullivan NWS Forecast Office was 2.34 inches, while a few miles south of the office only 0.31 inches was recorded. The image on the right is an automated analysis of rainfall reports.