From a blog entry on Weather Underground:
Tornadoes, violent thunderstorms, and torrential rains swept through a large portion of the nation's midsection yesterday, thanks to the strongest storm ever recorded in the Midwest. NOAA's Storm Prediction Center logged 24 tornado reports and 282 reports of damaging high winds from yesterday's spectacular storm, and the storm continues to produce a wide variety of wild weather, with tornado watches posted for Mississippi, Alabama, and Georgia, a blizzard warning for North Dakota, high wind warnings for most of the upper Midwest, and near-hurricane force winds on Lake Superior.
The mega-storm reached peak intensity late Tuesday afternoon over Minnesota, resulting in the lowest barometric pressure readings ever recorded in the continental United States, except for from hurricanes and nor'easters affecting the Atlantic seaboard. So far, it appears the lowest reading (not yet official) was a pressure of 28.20" (954.9 mb) reduced to sea level reported from Bigfork, Minnesota at 5:13pm CDT. Other extreme low pressures from Minnesota during yesterday's storm included 28.22" (956 mb) at Orr at 5:34pm CDT, 28.23" at International Falls (3:45pm), and 28.23" at Waskuh at 5:52pm. The 28.23" (956mb) reading from International Falls yesterday obliterated their previous record of 28.70" set on Nov. 11, 1949 by nearly one-half inch of mercury--a truly amazing anomaly. Duluth's 28.36" (961 mb) reading smashed their old record of 28.48" (964 mb) set on Nov. 11, 1998. Wisconsin also recorded its lowest barometric pressure in history yesterday, with a 28.36" (961 mb) reading at Superior. The old record was 28.45" (963.4 mb) at Green Bay on April 3, 1982. The previous state record for Minnesota was 28.43" (963 mb) at Albert Lea and Austin on Nov. 10, 1998.
The six most intense storms in history to affect the Great Lakes
According to the Chicago branch of the National Weather Service and Christopher C. Burt, our Weather Records blogger, the following are the six lowest pressures measured in the U.S. Great Lakes region:
1. Yesterday's October 26, 2010 Superstorm (955 mb/28.20")
2. Great Ohio Blizzard January 26, 1978 (958 mb/28.28")
3. Armistice Day Storm November 11, 1940 (967 mb/28.55")
4. November 10, 1998 storm (967 mb/ 28.55")
5. White Hurricane of November 7 - 9, 1913 (968 mb/28.60")
6. Edmund Fitzgerald Storm of November 10, 1975 (980 mb/28.95")