A strong thunderstorm developed over northern Ashland County and moved east across northern Iron County and into western Upper Michigan during the evening hours last Thursday, July 25, 2013. The storm developed quickly over northern Ashland County starting around 6:20 PM CDT and quickly moved east-southeast through Montreal and Pence, and into Gogebic County, MI by 7:15 PM CDT. The storm continued east-southeast across western Upper Michigan thereafter. These storms were part of a larger system that supported thunderstorms across much of the Northland.
The National Weather Service in Duluth investigated reports of wind damage in northern Iron County (Figure 2) and in Montreal (Figure 3). The survey team found sporadic tree damage along US Highway 2 starting 1.6 miles east of Saxon and in Iron Belt on State Highway 77. The damage area continued east-southeast through Pence and Montreal, to the eastern shore of the Gile Flowage, and into western Gogebic County, MI from 2.5 miles southeast of Norrie to 1.2 miles southeast of Van Buskirk. The observed damage included uprooted and broken trees. There was a concentrated area of damage associated with a locally stronger microburst in Montreal, where some structural damage occurred when trees fell on a couple of houses. Several parked cars in Montreal were also damaged by falling trees.
The overall damage path evolution was consistent with non-tornadic thunderstorm winds, or so-called "straight-line", wind damage, due to a downburst with wind speeds generally in the 50 to 60 mph range.
Note: Additional damage to the west and east of the surveyed area may have occurred during this thunderstorm.
Figure 1: Areal overview
Figure 2: Survey area
Figure 3: Montreal wind damage area
KDLH Radar image at 6:45 PM CDT zoomed over northern Iron County.
KDLH Radar image at 6:54 pm CDT zoomed over Montreal
Broken maple and birch trees on the eastern shore of the Gile Flowage
Uprooted tree south of County Road C