If you plan to enjoy Lake Michigan's beaches and waters this weekend, you will want to monitor the weather conditions.  The National Weather Service in Green Bay predicts that colder air will move over the relatively warm waters of the bay and Lake Michigan on Friday and Saturday, which can make for favorable waterspout conditions.  Waterspouts can be dangerous and cause significant damage to boats. They are more common in the morning or evening when cold, moist air moves across the lake's surface or when fast-moving pressure systems push air across the water.  The National Weather Service says you should monitor weather conditions this weekend and be prepared to seek shelter immediately if a waterspout appears to approach shore.