National Weather Service United States Department of Commerce

Documenting the July 4, 1999 BWCA Derecho



20th Anniversary of the Boundary Waters Canoe Area (BWCA) Blowdown Event

July 4, 2019 will mark the 20th anniversary of the historic Boundary Waters Canoe Area (BWCA) Blowdown event, which occurred over the midday hours of Sunday, July 4, 1999 across far northern Minnesota.  This event has become part of Minnesota weather lore in the 20 years since its occurrence, and likely represents a benchmark for something very near the extreme that the atmosphere is capable of producing.  In the blowdown event, nearly 500,000 acres of the Superior National Forest were almost completely flattened by intense thunderstorm winds estimated to have been between 80 and 100 mph, and hundreds of campers and paddlers that were in the Boundary Waters for the Independence Day Holiday Weekend were stranded in a maze of fallen trees and debris - many of them injured and in desperate need of assistance, only to be faced with the fact that all the ways in and out of the Boundary Waters were blocked by miles of fallen large trees.



Loop of radar reflectivity from the Duluth (KDLH) radar of the derecho moving through northeast Minnesota