Summary

A multi-day onslaught of thunderstorm complexes brought extraordinarily heavy rainfall and severe weather to central and southern Minnesota for the period June 21 through June 25. The heavy rains led to numerous reports of damaging urban and rural flooding. In addition to the torrential downpours, the thunderstorms spawned tornadoes, damaging winds, and hail. (see: compilation of storm reports). A tornado devastated the city of Buffalo Lake in Renville county during the evening of June 24.

Rainfall totals for the five-day period topped six inches along a 30 mile wide band stretching from Traverse county in west central Minnesota to Pine county in east central Minnesota. Total rainfall exceeded eight inches in some areas embedded within this swath. Rainfall amounts also surpassed six inches in some areas of Kandiyohi, Renville, Meeker, Wright, Sherburne, Hennepin and Chisago counties during the week.

Much of the rain in central Minnesota fell within a 48 hour period between June 22 and June 24. In Minnesota, the historical probability of receiving eight inches of rain within 48 hours for a given location is less than one percent per year. The heaviest rain in southern and east central Minnesota fell within a 12 hour period on June 24-25. The historical probability of receiving six inches of rain within 12 hours for a given location is less than one percent per year. (see: Rainfall Frequency Atlas of the Midwest.)

Radar-based precipitation estimates are occasionally limited by problems related to artificial returns due to ground clutter and hail, the interception of the radar beam by intervening precipitation, and the curvature of the earth. However, for the storms of June 21-25 the radar-based precipitation estimates compared quite well with ground-based data gathered by volunteers working with Soil and Water Conservation Districts, the Metropolitan Mosquito Control District, and the National Weather Service. To provide the greatest amount of spatial detail possible, radar-based images are offered in this narrative.

The image below provides a multi-day estimate of precipitation values for the period 7:00 AM, Saturday - June 21 through 7:00 AM, Thursday - June 26. The data are provided by the WSI Corporation's (http://www.intellicast.com) analysis of National Weather Service radar imagery. To create this image, five distinct 24-hour precipitation total images were summed using graphical techniques developed by the State Climatology Office.

Heavy Rain - June 22 and 23

For many areas of central Minnesota, the heaviest rain fell during the evening hours of Sunday, June 22 and into the early morning of Monday, June 23. 24 hour totals in excess of six inches were reported in northern Morrison, southern Aitkin, and northern Kanabec counties. The largest 24 hour total reported was 7.00 inches in Pulaski Township of Morrison county.

Heavy Rain - June 24 and 25

In southern and east central Minnesota, the heaviest rainfall fell during the evening hours of Tuesday, June 24 and into the early morning of Wednesday, June 25. 24 hour totals in excess of six inches were reported in western Renville, eastern Wright, southern Sherburne, central Hennepin, and central Chisago counties.

The map at right was compiled using rainfall measurements made by volunteer observers located throughout east central Minnesota. The largest 24 hour total reported was 8.19 inches in Elk River of Sherburne county. Some of the larger rainfall totals in the metropolitan area for June 24-25 include:

Sherburne county	Hennepin county
Elk River - 8.19"	Plymouth - 6.68"
	Brooklyn Park - 6.50"
Wright county	Brooklyn Center - 6.00"
Monticello - 7.50"	downtown Mpls. - 5.90"
Buffalo - 6.25"	New Hope - 5.83"
Rockford - 4.50"	Robbinsdale - 5.75"
Cokato - 4.19"	south Mpls. - 5.55"
	St. Louis Park - 5.28"
Anoka county	Maple Grove - 5.14"
Fridley - 5.32"	Corcoran - 5.00"
	Hassan - 4.80"
Ramsey county	Champlin - 4.71"
St. Paul midway - 4.98"	Golden Valley - 4.70"
St. Paul (Como) - 4.65"	Dayton - 4.60"
Maplewood - 4.59"
Little Canada - 4.55"	Chisago county
Falcon Heights - 4.52"	North Branch - 6.00"
St. Paul (Holman) - 4.31"	Taylors Falls - 4.00"
Vadnais Heights - 4.17"
White Bear Lake - 4.10"	Washington county
Shoreview - 4.07"	Scandia - 4.71"
	Forest Lake - 4.01"

The State Climatology Office thanks the Soil and Water Conservation Districts, the Metropolitan Mosquito Control District, the National Weather Service, and all of the diligent volunteer precipitation observers who make analyses of these events possible.

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URL: http://climate.umn.edu/doc/journal/flash_floods/ff030622-25.htm
Last modified: June 26, 2003