Here is the latest from the National Weather Service.
The National Weather Service in Billings has issued a Flood Watch
for the following rivers in Montana...

  Yellowstone River at Billings affecting Stillwater and Yellowstone
  Counties

.High elevation snowmelt along with periods of rainfall through
tonight may result in flooding along the Yellowstone River near
Billings by Thursday night. Bank erosion is likely. High river flows
will likely continue into early next week as another period of warming
temperatures is expected late in the week with additional rainfall
possible over the holiday weekend.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Watch means that flooding is possible. Now is the time to
prepare for action in the event flooding occurs. Bank erosion is likely.
Do not walk near river banks as the underlying soil may be eroded.
In addition, if encountering flooded roads, Turn Around Don`t Drown.