* WHAT...North winds to 20 kt and significant waves to 6 ft expected. * WHERE...Northerly Island to Calumet Harbor IL and Calumet Harbor IL to Gary IN. * WHEN...Until 7 PM CDT this evening. * IMPACTS...Conditions will be hazardous to small craft. * ADDITIONAL DETAILS...The highest waves are expected to remain offshore and near and east of the Illinois and Indiana state line. Inexperienced mariners, especially those operating smaller vessels, should avoid navigating in hazardous conditions.