Snow Rules!

Enhanced Snow and Precipitation Monitoring within Minnesota Portions of Watersheds Draining to Lake Superior

Minnesota’s Lake Superior Coastal Program

2005-06 Snow Totals

The 2005-06 snowfall, in inches, is shown in the above map. Twenty-one general snowfall events lasting from just a day or so, to the better part of a week semi-continuous snowfall, were identified during the 2005-06 season.

To make the best use of data, each month of snowfall was analyzed to a grid of values for the region. Those monthly grids were then summed to form the pattern shown above. The formation of grids of snow was guided by the use of elevation and the distance to Lake Superior. In that way even in areas where data is still somewhat sparse the steep ‘gradient’ of snowfall values, up to about ˝ foot per mile, from shore to inland could be shown.

Data was provided by 63 Soil and Water Conservation District Observers plus 27 National Weather Service and DNR observers (in St. Louis, Lake, and Cook counties).

2005-06 'events'

Location of 'peak' snow fall

Snowfall deposition varies from the shore of Lake Superior to points inland. The pattern arises from both changes in the availability of moisture as well as from elevation changes. Lake Superior, largely ice free for most of most winters, supplies moisture to cold, dry air flowing across its surface. That moisture can be precipitated out when the air is recooled as it is lifted when it flows uphill as air crosses the shoreline.

The blue dots, representing individual observers, show the average fraction of the median of the event's non-zero snowfalls. The green line is a type of weighted running average of the individual observer values. An overall peak occurs approximately 8-10 kilometers inland. That distance is where the land surface has climbed about 75% of the height difference of the inland highest surfaces and the Lake Superior. On the average the highest elevation of the land surface occurs at about 25 km inland. The location of that snowfall approaches the elevation peak but still on the upslope side is what was expected.

The graph can be stretched logarithmically so that the observers nearest the shore are more spread out in the graph.

4-season average snowfall (2002-06 season)

2004-05 Season

Event maps and additional analysis was done for the 2004-05 season.

2003-04 Season

Event maps and additional analysis was done for the 2003-04 season.

2002-03 Season

The 2002-03 season map can be viewed as well.

Snow Rules! main page
State Climatology Office, DNR - Waters, 2006
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