National Weather Service United States Department of Commerce

Cold Front Dropping South Across the Western U.S.; Watching Threat for Tornadoes and Flooding in the South

A cold front will push south across the Western U.S. into Tuesday with mountain snow and areas of gusty to high winds. An area of low pressure will form along this front on Tuesday and bring a potential for severe thunderstorms with tornadoes and excessive rainfall in the lower to mid Mississippi River Valley. To the north, heavy snow is possible in parts of the upper Midwest. Read More >

Downburst Crosses KLOT Doppler Radar 6/29/2012


On the evening of June 29, 2012, a severe thunderstorm spawned a downburst which resulted in a swath of 75 to 95 mph winds across portions of central and eastern Kendall and northern Will Counties. Numerous damage reports were received which included downed power lines, uprooted trees, broken tree limbs, as well as some structural damage.  The storm passed right over the KLOT Doppler Radar which resulted in an optimal Doppler Radar measurement of the wind speeds.  The images below show the progression of the storm as it approached and crossed over the radar.  The green and blue colors on the velocity images show wind blowing toward the radar, while the red and orange colors show winds blowing away from the radar.  As the storm approaches the radar, the radar beam samples winds closer to the ground.  Click on the images to see a larger version.


925 PM: Reflectivity (left) and Velocity (right) - approximate wind speeds ~ 1170 ft AGL 

Reflectivity at 925 pm

Velocity at 925 pm


939 PM: Reflectivity (left) and Velocity (right) - approximate wind speeds ~ 440 ft AGL

Reflectivity at 939 pm

Velocity at 939 pm


949 PM: Reflectivity (left) and Velocity (right) - approximate wind speeds ~ 110 ft AGL

Reflectivity at 949 pm

Velocity at 949 pm


951 PM: Reflectivity (left) and Velocity (right) - approximate wind speeds ~ 150 ft AGL

Reflectivity at 951 pm

Velocity at 951 pm

A sample of the highest reported wind speeds.  


Wind Speed (mph)

5 miles south of Oswego


NWS office in Romeoville




2 miles NW of Lockport


MDB/KJB 6/30/2012