Storms erupted to life once again the morning of Sunday, July 1st for the Chicagoland area thanks to a gravity wave caused by collapsing storms in Iowa colliding with a frontal boundary that has been wobbling across the area the past couple days. The image below shows how it all happened. Click for full size.
The storms quickly grew severe, with already high values of instability in the area due to the hot and humid airmass. Despite being only 11am, CAPE values [which measure energy in the atmosphere] were already at an impressive 3000 j/kg. The storms began producing damaging winds in parts of Dupage, Kane and Kendall counties. As damage reports began pouring in, the NWS in Chicago issues a severe thunderstorm warning that mentioned the potential for 100mph winds!
AT 1222 PM CDT…NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING QUARTER SIZE HAIL…AND EXTREME DAMAGING WINDS IN EXCESS OF 100 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM ELK GROVE VILLAGE TO ELMHURST TO DOWNERS GROVE TO NAPERVILLE…AND MOVING EAST AT 45 MPH. THE MOST INTENSE WINDS WERE MOVING EAST ACROSS CENTRAL DUPAGE COUNTY
The storms were heading for Chicago and I prepared to document them at home near Midway Airport. Despite the warning, the damage ended up not being too extreme. An initial brief gust to possibly 65-70mph brought down lots of small branches and limbs off trees, sent garbage cans and lawn furniture flying as well as causing a brief power outage. Dime size hail fell for less than a minute, and after the half hour onslaught it was over. It appears the south side of Chicago got skirted by the worst of the action as damage north and west of the city is much worse.
This was just the latest round of storms in what continues to be an active pattern. Looking at the week ahead, not much is to change as the area is still expected to be locked in a hot, humid airmass. There will be a continued threat for these kinds of storms for much of the week, though providing details on specific locations is tough.
Photos and Radar Images.
More storms are expected later, stay tuned!