EF2 tornado in Cook County, Minnesota

A rare late-season strong tornado caused tree damage

across parts of the Boundary Waters Canoe Area Wilderness in

northern Cook County. The tornado appeared to begin on Alder Lake,

initially causing damage near Campsite #3 where a small swath of

trees were downed, several snapped halfway down their trunks. The

tornado then traveled north causing sporadic damage until just north

of Rocky Lake where there was a more concentrated area of downed

trees roughly 270 yards across. Sporadic tree damage continued until

reaching Clearwater Lake and crossing the lake just west of Campsite

#5, causing significant damage north of Clearwater Lake and north to

the International Border (Mountain Lake). Significant tree damage was

observed along the Border Route Trail, of which passage was made

impossible as the tornado reached its maximum width of around 500

yards as it moved across the trail. Numerous trees were snapped near

their bases within this area of damage. The coverage of damage was

widespread with satellite imagery depicting over 80% of trees

uprooted, bent, or snapped across its path near the Border Route

Trail. The tornado then crossed the International Border and continued into Northwestern Ontario, Canada. No private property was damaged along the course of the tornado.

The National Weather Service appreciates the public reports, photos,

and videos of this tornado damage, aerial photographs from the US

Forest Service, and satellite imagery shared by the Northern

Tornadoes Project (Western University in Canada) which all aided in

an accurate assessment of the damage.

An area of low pressure working across the Upper Midwest on the 10th was able to pull abnormally high moisture into the region leading to sufficient instability for the development of storms. An upper jet was also over the area contributing to higher than normal amounts of shear as well resulting in some of the storms becoming severe across the region. Isolated reports of large hail and damaging winds were received along the North Shore of Lake Superior along with a rare October tornado that developed over the Boundary Waters Canoe Area Wilderness and tracked northward into Canada.