A strong line of storms is whipping across the Great Lakes on Thursday afternoon. In the radar reflectivity above, you can see the bow echo’s comma head take shape and begin to spin — these features have been known to produce extremely strong downdrafts as well as tornadoes.
While it has weakened some as it crossed over the cool water of northern Lake Michigan, the storm has prompted a large severe thunderstorm warning for Michigan cities including Manistee, Frankfort, and Arcadia.
Winds gusted to around 40 mph as the storm passed over Green Bay, Wisc.
This complex of storms actually began to take shape over North Dakota in the early morning hours on Thursday.
Another look at the Derecho coming across lake Michigan. pic.twitter.com/rl8f2XZ0JM— Henry Margusity (@HenryMargusity) September 4, 2014