HELENA — Most of Montana's waterways were exceptionally low after a dry winter and a cool spring that kept much of that potential water locked up in the mountains in the form of snow. However, the situation has significantly changed.
Historic flooding is ongoing in southern Montana. Heavy rain and warmer temperatures combined to release water from the ample mountain snow for a compounded flooding situation. While most of the severe flooding is in the Yellowstone River drainage right snow, the upper Missouri is also flooding and near record-high levels. The Gallatin river is under a flood warning and the madison and Jefferson are on the rise. Water flows downstream, and the water will be heading down the Missouri. Already in the last month, Canyon Ferry Lake has seen the water pool rise by nearly 10 feet, and this is before the upstream flooding arrives.
Areas along the Rocky Mountain Front including the Dearborn, Sun, Teton and Marias rivers are still only between the 25th and 75th percentile of historic streamflow, meaning closer to average. However, heavy rain and more melting snow will fill these waterways up as well. After this storm, temperatures will climb into the 80s and 90s late this week which will melt even more snow.
Water, water everywhere and there's more to come. It will take some time to drain down into the Missouri mainstream, but it's coming.
Use caution around fast-moving, cold water in the coming days.