Freezing rain, heavy snow, and blizzard conditions were experienced across the upper Midwest during this event of Friday, 2005 January 21st. Much of far north central United States saw nearly 24 hours of continuous snowfall. Areas further south, including southwest Minnesota and eastern South Dakota, saw precipitation mainly in the form of freezing rain, accompanied by only a few inches of snow.
This event was a result of a large low pressure system that tracked southeast through southern Canada, across Montana, through the Dakotas, and finally across far southwest Minnesota. This system also continued to track southeast through Iowa, before moving into the Chicago area.
The snow associated with this system was due to a feature called an inverted trough. This is an elongated area of low pressure, or trough, that extends northward from a low pressure center. As the low pressure center tracked across southwest Minnesota and along the Minnesota-Iowa border, the inverted trough pushed eastward through Minnesota and into Wisconsin. Since the precipitation occurred ahead of the inverted trough, this was an "ahead case".
Another factor with this event were the very strong winds, which resulted in blizzard conditions across eastern North Dakota and northwest Minnesota. These winds were a result of a very sharp change in atmospheric pressure. This large pressure gradient was due to the exiting area of low pressure to the southeast, contrasting with the large area of incoming high pressure to the northwest. |
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