Houghton, Michigan – A transition from rough to dangerous marine conditions is underway across Lake Superior’s southern shore Tuesday as westerly winds shift north, intensifying into a gale by nightfall. The National Weather Service in Marquette has issued a Small Craft Advisory through 5 p.m. Tuesday, followed immediately by a Gale Warning from 5 p.m. Tuesday to 8 a.m. Wednesday for waters between Manitou Island and Point Isabelle.
According to the weather service, early-day west winds of 10 to 20 knots with gusts near 30 knots are already producing waves of 5 to 8 feet. Conditions will worsen after sunset as north winds strengthen to 15 to 25 knots, gusting to 35 knots with similar wave heights.
Forecasters warn of hazardous seas and sharply reduced visibility in blowing spray and intermittent showers. Mariners are urged to remain in port or seek protected harbors until winds subside Wednesday morning. The U.S. Coast Guard Station Portage advises boaters to secure lines and gear, and avoid nighttime transits near Manitou Island, Bete Grise Bay, and Point Isabelle where wave action will be strongest.
Conditions are expected to improve gradually after dawn Wednesday, with lingering swells and choppy surf near the Keweenaw shoreline. Another round of blustery weather may return late Thursday as fall storms continue to track across the Upper Great Lakes.