GREAT FALLS — An ice jam along the Missouri River in Great Falls is being monitored by the National Weather Service and public-safety officials.
The NWS says that an ice jam in the area of River Drive from the 9th Street Bridge south to the Warden Bridge (10th Avenue South) could cause flooding at any time through Wednesday, January 1st.
Of particular concern is the area between Central Avenue (1st Avenue North Bridge) and Broadwater Bay, which is usually the first area to be covered by rising water in such situations.
They caution that if there is water on the road, you should turn around and never attempt to drive through it.
The National Weather Service website says: "Flooding could develop along the Missouri River in Great Falls because of an ice jam. As of 5am Tuesday, the river height was approaching 15 feet, above which we could start to see flooding low lying areas along the River, including River Drive and the River’s Edge Trail system. Since ice jams are unpredictable, water can back up or release quickly. Don’t drive around barricades or through a flooded road. A flood watch is in effect for this area. Continue to monitor for further updates on our Facebook page, Twitter page, and the NWS Great Falls website."
The website SciJinks.gov explains: "Ice jams are caused by melting snow and ice in the springtime. Warm temperatures and spring rains cause snow and ice to melt very rapidly. All this extra water causes frozen rivers and streams to swell up, and the layer of ice on top of the river begins to break up. The rushing river carries large chunks of ice downstream, and sometimes a group of ice chunks get stuck in a narrow passage of the river. The ice chunks form an ice jam, which blocks the natural flow of the river."
According to Weather.gov, Montana has the largest number of reported ice jams in the 48 contiguous states, and also the most ice-jam related deaths in the contiguous U.S. Ice jams can develop quickly and cause significant flooding or flash flooding. Two-thirds of Montana's ice jams occur in February and March.