Big temperature changes cause ice jams

There is a hydraulic outlook for central and western Indiana for Thursday as temperatures warm and ice jams become possible on rivers. Ice jams can cause flooding, and are usually seen most in the spring, but with a temperature swing this big, it is now possible in January. Ice jams are most common in small winding rivers and tributaries, rather than large rivers with locks and dams.

Ice jams occur when temperatures make a big warm up after a prolonged period of freezing temperatures. Ice that forms on the rivers will start to break up and melt in spots, and float downstream. Then, ice chunks get jammed on unfrozen ice sheets downstream, usually near a river bend. If it rains, the water level in the river will rise, because the water cannot freely float downstream past the ice jam. This can result in flooding.

Much of the river ice in Michiana has melted already, so ice jams should not be a big issue in Michiana in the coming days.