Enhanced Snow and Precipitation Monitoring within Minnesota Portions of Watersheds Draining to Lake Superior
To make the best use of data, each month of snowfall was analyzed to a grid of values for the region. Those six 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 46 Soil and Water Conservation District Observers plus about 20 National Weather Service and DNR observers.
The 'drift=' information at the top of each event map shows what factors fit the pattern of snowfall best for that event. Possible factors include elevation, distance from the Lake Superior shore, UTM X or Y (simple geographical location).
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 pink curve in the graph above shows a highly idealized ‘average’ elevation (in kilometers) of the Duluth to Canada portion of the Lake Superior ‘highlands’ as distance from the shore increases. The blue dots, representing individual observers, show the average fraction of the event maximum snowfalls. The green line is a type of running average of the individual observer values. An overall peak occurs approximately 8-10 kilometers inland. The location of that snowfall peak near the elevation peak but still on the upslope side is what was expected.
, DNR - Waters, 2004-5
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