After a “ washout” Wednesday, a potent spring storm passing south of Chicago will batter the area with extremely high winds Thursday. North winds, expected to gust as high as 60 mph, blowing down the length of Lake Michigan will create huge waves, not only flooding areas along the lakeshore, but likely produce damage to trees, power lines and some structures. Adding to Thursday’s misery will be chilly temperatures hovering near 40 and periods of rain, possibly mixed with snow. Wind will decrease Thursday night and Friday as the storm departs, setting the stage for a rapid warm-up. The mercury will show modest increases into the lower 50s Friday and the lower 60s Saturday before surging well into the 70s over the weekend. An approaching cold front will trigger showers and thunderstorms on Monday, followed a return to more seasonable readings in the 50s and 60s.