MISSOULA — The National Weather Service has issued a Flood Watch due to ice jamming for the Lemhi River near Lemhi, ID until further notice.
Ice jams are formed as a result of long cold spells that cause portions of rivers and streams to freeze. Fluctuations in temperature or water level can break the ice into chunks which can jam at any obstruction as they move downstream. These jams dam the water resulting in flooding upstream and can release very suddenly causing a surge of flooding downstream.
As of 1pm Thursday, the stage was 7’ and it continues to fluctuate between 6.5’ and 7’. Flood stage is 6.5’ and record flood stage is 7.2’. At 7’, expect likely flooding along Highway 28 from Tendoy to Salmon. At 8.5’, possible damage to irrigation diversion headgates and ditches is possible.
In addition, the Salmon River is also experiencing a large ice jam extending from roughly Maxwell Lane north through the town of North Fork. Flooding is impacting the Wagonhammer campground and other low-lying properties along this stretch of the river, and may become more widespread as ice continues to back up.
Temps will continue to remain below freezing at night keeping river ice an impact in both the Lemhi & Salmon Rivers.
If you are in the watch area, remain alert to possible flooding. Please report observed flooding to local emergency services or law enforcement and request they pass this information to the National Weather Service when you can do so safely.
