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Heavy Lake Effect Snow, Duluth, MN

December 4, 2007

What began as a few lake flurries at 3 AM would soon be the most impressive lake-effect snow event to date since this observer arrived in Duluth in late summer 2001. Flurries increased to accumulating snow showers starting around 7:45 AM. Light snow from a short wave trough embedded in the northwest upper-level wind flow began falling shortly after 10 AM. From that point on, a narrow mid-lake band of snow from east-northeast winds off the lake rapidly intensified. Snowfall rates underneath the core increased to 2 inches or more per hour.

The heavy snow band remained for the most part in place affecting Central into West Duluth from downtown to where Interstate 35 rises up Thompson Hill. The northern edge teased this observer's location for most of the event. Early in the afternoon however the dead center core of the band moved overhead for two hours, dropping about 4.5 inches of snow. As the heaviest snow began, the sky grew unusually dark. Lights inside buildings could easily be seen. At one point in time, the snow was so heavy that flow traffic along a nearby major four-lane road stalled. Big, fat, fluffy "lake flakes"!

Early in the evening the lake-effect snow band weakened and drifted south out of the city. Only very light snow or flurries from the clipper-type system lingered through the evening. The National Weather Service office measured 5 inches, but much more fell in some other places. An off duty National Weather Service employee measured 16.8 inches in the vicinity of 59th street in West Duluth. The author of this summary measured 8.5 inches. It is likely that higher amounts fell in a few spots. Personal contacts in some areas of the city not affected by the snow band only received 1 to 2 inches.

Lake effect snow events of this magnitude in such a short period of time are not common in Duluth, MN. The lake convection was unusually strong for an east type wind event off Lake Superior. In an Area Forecast Discussion out of the National Weather Service in Duluth, the forecasters noted that radar showed echo tops up to 7,500 feet. The highest snowfall rates exceeded 2 inches per hour. The radar images show how localized the band was.

Radar images from the National Weather Service in Duluth, MN

2:36 PM CST December 4, 2007

3:29 PM CST December 4, 2007

7:19 PM CST December 4, 2007