* WHAT...Waves will quickly build from 1 to 2 feet tonight to 3 to 4 feet Thursday. The highest waves will be in southern Berrien County. Dangerous swimming conditions are expected with north- northeast winds creating strong a southward flowing longshore current and strong structural current, especially on the north side of piers and breakwalls. Rip currents are possible. * WHERE...Northern Berrien and Southern Berrien counties. * WHEN...From 2 AM EDT Thursday to 8 PM EDT Thursday. * IMPACTS...Strong currents can pull swimmers into deeper water and high waves can sweep people off piers.