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Showers and thunderstorms, some over 55,000 feet tall, produced scores of severe reports logged by the Storm Prediction Center. As of 10 p.m. reports included 6 tornadoes, 3 in Nebraska and 3 in Iowa, 38 large hail reports, including baseball sized hail near Craig, Iowa (in the northwest corner of the state), and 38 reports of damaging winds. Among the higher gusts, all in Iowa, were 75 mph at Lamoni, 70 mph at Prescott, and 61 mph at the Ottumwa Airport. In addition to the severe weather, flooding downpours accompanied the large complex of storms. Guthrie Center, Iowa recorded 4 inches of rain in just 3 hours causing local flooding. Stormy weather is headed toward the Chicago area and is expected to arrive predawn Wednesday.
 

With an intense low pressure system located over far southern Lake Michigan this morning, the city's official barometer at O'Hare Airport dropped to extremely low levels with  a reading of 28.91inches (979 millibars) at precisely 7:39 am CST. By 9 a.m. the pressure had risen to 28.93 inches, a sign that the low was beginning to depart.

 According to records provided by Chicago climatologist Frank Wachowski this is the lowest air pressure logged here in nearly 20 years since October 17, 1990 when readings fell to 28.81 inches (976 millibars). Readings this low here are quite rare and are recorded only in the most intense storms. To put this low barometer reading in perspective it is the typical pressure observed for hurricanes straddling  the Category 1-2 threshold with highest sustained winds just under 100 mph.

The city's all-time lowest barometer reading on record is 28.70 inches (972 millibars) observed on March 12 1923. In comparison the world's lowest barometer reading was 25.69 inches (870 millibars) recorded on Oct. 12, 1979 520 miles northwest of Guam in the eye of Typhoon Tip.

The cold front associated with low pressure in southern Minnesota moved through
Chicago between 6:30 and 7PM this evening preceded by a line of showers and
thunderstorms. The line of storms and cold front extended from Milwaukee south just off
the Lake Michigan shoreline all the way south to Terre Haute, Indiana. Southeast winds
ahead of the front shifted abruptly southwest at 15 to 25 m.p.h.

-Paul Dailey WGN-TV Meteorologist