There is an ice jam on the Gallatin River already causing flooding south of Gallatin Gateway. Flood Warning is in effect until 6pm Sunday night. Details here:

At 610 PM MST... emergency management reported an ice jam causing
minor flooding in northern Gallatin County... a half mile south of
Gallatin Gateway. Rising water is threatening homes along the
Axtell-Gateway Road and several homes on The Gateway south Road.
Water is running across the Axtell-Gateway Road which is closed
from Deer Spring Road to Gateway south Road.

Flooding will remain over mainly rural areas of northern Gallatin
County.

Most flood deaths occur in automobiles. Never drive your vehicle into
areas where the water covers the roadway. Flood waters are usually
deeper than they appear. Just one foot of flowing water is powerful
enough to sweep vehicles off the Road. When encountering flooded
roads make the smart choice... turn around.