Wet Fall and Wet Winter Enhances Flood Potential

The fall months of September through November 2008 were the wettest of record in both Fargo and Grand Forks. Since then, moderate to heavy snowfall has occurred, with the higher amounts in the southern Red River Valley, Upper Sheyenne River and Devils Lake Basins. While the wet fall, on its own, is not an indicator to significant spring flooding, the additional of heavy winter snowfall is a second important factor.

As a result, the North Central River Forecast Center (NCRFC) in Chanhassen has indicated the likelihood of significant river flooding this spring season. Residents are advised to read this article "Anatomy of a Red River Spring Flood" by Senior Meteorologist Al Voelker. Although it was written several years ago, the article is still very relevent. One other factor that is also critical, and not covered by the current article, is Land Use Modifications. 

In the past 40 years there have been 4 major flood events in the Red River Valley of the North. The spring floods of 1969, 1979, 1989 and 1997 were devastating, each one having a greater impact than the previous one.  Research by the U.S. Army Corps of Engineers has identified one of the more significant contributors to flooding on the Red River. Land Use Modifications including the enlarging of ditches, development of diking, and extra drainage allows water to reach the main-stem Red River more quickly than before. As a result, residents of the Red River Valley proper have seen higher flood levels with lower amounts of precipitation. The basic premise of Mr. Voelker's remains valid; a wet fall, heavy winter snows, late and/or rapid melt along with rainfall near the melt are significant factors contributing to major flooding. The four years mentioned above had some or all those factors come into play.

The development of the Advanced Hydrologic Prediction Services (AHPS) incorporate all these factors and more into the prediction of river levels. This has allowed the NWS and our partners in the Emergency Management community, flood fighters and those whose jobs are to protect life and property, a tool to better assess the probability for flooding weeks and months in advance.

Below are tables that rank the 10 highest snowfall and liquid precipitation periods in Fargo and Grand Forks, between September 1st through February 28th. These are preliminary data from the National Climatic Data Center and subject to modifications at a later date. However, they do indicate the Fargo and Grand Forks area are experiencing the wettest six month fall and winter period on record. It is critical to note that this is in large part due to the record wet fall months of September - November 2008. It is also important to note that the seasonal snowfall to date is in 10th place for Fargo, but not in the top 10 for Grand Forks.

Fargo Area            
Total precipitation Sep-Feb   Total snowfall Sep-Feb    
Years 1885 - 2009     Years 1885 - 2009    
Rank Value Year Missing Rank Value Year Missing
1 14.31 2009   1 83.4 1997  
2 12.15 1897   2 71.5 1897  
3 12.00 1904   3 66.1 1994  
4 11.61 1972   4 63.4 1937  
5 11.36 2001   5 60.3 1989 (1)
6 11.34 1978   6 59.4 1996  
7 11.25 1882   7 55.3 1982  
8 11.11 1883   8 53.8 1907  
9 11.02 2005   9 52.6 1986  
10 10.58 1999   10 51.2 2009  
               
Grand Forks Area            
Total precipitation Sep-Feb   Total snowfall Sep-Feb    
Years 1893 - 2009     Years 1893 - 2009    
Rank Value Year Missing Rank Value Year Missing
1 13.12 2009   1 76.8 1996  
2 10.26 1982   2 69.9 1997 (6)
3 10.11 1974   3 64.0 1989  
4 9.37 1966   4 62.6 1986  
5 9.24 1999   5 59.0 1999  
6 9.15 1978   6 50.5 1994  
7 9.05 2001   7 50.3 1956  
8 9.02 1932 (5) 8 48.5 2004  
9 9.01 1901   9 44.7 1948 (1)
10 8.52 1996   10 44.5 1936 (2)
The numbers in parenthesis indicate the number of missing days during the period indicated.         

It is because of the record precipitation and above normal snowfall that your NOAA's NWS is alerting the residents of the Red River Valley of the North of the potential of major flooding this 2009 spring. Stay tuned to your favorite source of weather information as well as NOAA's All Hazards Weather Radio and our web site for later updates and important information.

Contact the NWS in Grand Forks at 701.772.0720 for more information.. 



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