Climatic Conditions Leading to the Spring Flooding of 2001

Major flooding occurred along many of Minnesota's rivers during April 2001. The flooding was caused by four contributing climatic factors:

contributing climatic conditions

  1. significant autumn precipitation
  2. heavy winter snowfall
  3. less than ideal snowmelt scenario
  4. record-breaking April precipitation

1) significant autumn precipitation

Many southwestern, central, and east central Minnesota locations entered November with water deficits due to below normal growing season rainfall. However, heavy early November rains filled the upper portions of the soil profile before soil freeze-up. The figures below show that November 2000 precipitation exceeded the historical average by more than two inches in many locations.


2) heavy winter snowfall (2000-2001)

Mid and late-November snows blanketed much of the state with a lasting snow cover that was to persist into the early spring. The figure below shows that seasonal snowfall totals exceeding 60 inches were common throughout western and southern Minnesota. Snowfall totals in excess of 72 inches were reported in northeastern Minnesota. As seen below, snowfall totals in 2000-2001 ranked above the 80th percentile across much of southern, western, and northeastern Minnesota. In some communities, seasonal snowfall exceeded the 95th percentile. Normal annual snowfall in the southern one half of Minnesota ranges from 36 inches in the west to around 50 inches in the east. 2000-2001 snowfall topped the historical average by approximately two feet in western Minnesota, and by more than 18 inches in most southern Minnesota counties. Snow water equivalent in the snow pack at the end of the season was three to five inches in many areas. While 2000-2001 snowfall was heavy in many communities, the snowfall totals were far less than the 72 to 96 inch totals that covered most of the Red River basin and much of the upper Minnesota River basin in 1997.

3) less than ideal snowmelt scenario

The winter of 2000-2001 provided very few mid and late-winter melting days. While January was relatively mild, temperatures were still cold enough to retain most of the snow cover established during November and December. February was quite cold, finishing four to eight degrees below normal. March temperatures were three degrees below normal. The snow pack gradually diminished in depth throughout March, nevertheless snow water content did not change appreciably. Much of the melt water stayed on the landscape in the micro-relief.

4) record-breaking April precipitation

Extraordinarily heavy precipitation fell across much of Minnesota in April 2001. The figure below shows that a broad swath of southwestern, central, east central, and northeastern Minnesota received over six inches of precipitation from April 1 to April 23, 2001. Precipitation totals surpassed the historical average by more than four inches in these areas. For many communities, all-time April monthly precipitation records were set before the month came to a close.

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URL: http://climate.umn.edu/doc/flood_2001/flood_2001.htm
Last modified: April 24, 2001