When it comes to extra-tropical low pressure systems across the Great Lakes and Midwest, the months of October and November can be some of the most active ones. Extra-tropical lows are the storm systems usually notated as a red letter "L" on surface weather maps. Not only do they simply bring lower barometric pressure, but they can also bring strong winds, sharp temperature contrasts, and, if the conditions are cold and windy enough, blizzards. One notable autumn blizzard from the fairly recent past is the Halloween Blizzard of 1991, which brought over 3 feet of snow to Duluth, MN and 28.4" to the Twin Cities. Further back in time, another even stronger low pressure system struck the Midwest on Armistice Day (now called Veterans Day) November 11, 1940.
Source: NWS-La Crosse
The Armistice Day storm was responsible for the deaths of 144 people, many of whom were duck hunters who became stranded out on the Mississippi River when the temperature plummeted and whiteout conditions ensued. Out ahead of the storm system, earlier that day, conditions were mild with temperatures in the 50s and even some 60s into Illinois. These warm conditions proved to be an enticing deception to the duck hunters, many of whom had been off from school or took off from work to take advantage of the optimal conditions. On the morning of November 11, a low pressure system, which had initially brought gusty winds to the Pacific Northwest, had now reached central IA. Behind the cold front associated with this system, temperatures had already plummeted some 50 degrees across portions of South Dakota and Nebraska, and blizzard conditions had set in. Unfortunately, the timing of this system, with the sharpest temperature drop coming near midday, as well as a poor forecast by the Weather Bureau at that time, contributed to a large loss of life with this storm.
Source: Minneapolis Star Journal
As the cold, polar air started to work in behind the low, and the system raced northward to Lake Superior, so too did the heavy snow and whiteout conditions. Visibility was so poor that one survivor remarked when riding in the front seat of a car, there were times you couldn't even see the hood ornament. Hunters who had dressed relatively lightly, due to the early-day mild temperatures, now had to contend with near hurricane-force wind gusts and heavy snow out on the Mississippi. Many froze to death either on islands in the river where they sought refuge, or drowned in trying to reach shore in the strong winds. 66 sailors also died on five different ships which sank on Lake Michigan at the height of the storm. In Minneapolis, people abandoned their cars and by daybreak the following day, the snow was drifted up to near the top of car roofs.
Source: Stearns History Museum
After the poor advance warning/forecast that the United States Weather Bureau had provided, a restructuring of the organization took place. Before the storm, District Forecast Centers still had responsibility for large geographic areas. For example, the Chicago office issued four forecasts per day for Illinois, Indiana, Iowa, Michigan, Wisconsin, Minnesota and North and South Dakota. In the aftermath of the storm, Minnesota would get its own 24-hour forecast office as well as a larger staff. Weather observing and forecasting technology has increased a great deal over the past 75+ years. Satellites and radar provide nearly real-time snapshots of cloud and precipitation patterns. Add to that supercomputers and the Internet, and the scientific wonder that is numerical weather prediction becomes a reality. The public is also able to receive forecasts much more readily via TV, smart phone, Weather Radio, etc.
Extra-tropical cyclones as strong as the Armistice Day storm have and still do occur even as recently as 2010. Between October 26 and 27, 2010, a strong low pressure system, with a central pressure even lower than the 1940 storm, whipped up winds, waves, and snow across the Great Lakes. Fortunately, there was only 1 fatality in this storm, not only because of better forecasting, but also because this storm didn't have air nearly as cold moving in behind it. However, the memory of the 1940 storm, as well as the more recent 2010 example, show how autumn can bring wicked wintry weather to the nation's midsection.
*More links on the Armistice Day storm:
http://www.youtube.com/watch?v=ZtYJPv6elPM (A first-hand account of a duck hunter who got caught out in the blizzard)
http://www.mnvideovault.org/mvvPlayer/customPlaylist2.php (Twin Cities Public Television segment on the storm)
http://www.weather.gov/arx/nov111940 (Excellent, in-depth site from NWS-La Crosse)