The National Weather Service office in Great Falls issued a hydrologic outlook Thursday morning flagging the potential for significant flooding across western North Central Montana this weekend, with heavy rainfall expected to begin Saturday and taper off Monday.

Forecasters are warning of rainfall rates around 0.50 to 0.75 inches every six hours over a 36-hour stretch, with total accumulations of one to two inches across most affected areas. That kind of sustained rainfall on ground that is already saturated from spring snowmelt raises the risk of rapid rises on area streams and creeks — including drainages that feed into the Missouri River system near Helena.

Residents in low-lying areas, particularly those near Prickly Pear Creek and other local drainages, should monitor conditions closely through the weekend. The NWS Great Falls office will issue updated watches or warnings as the system moves in. Lewis and Clark County emergency management recommends that property owners in flood-prone areas take precautionary steps before Saturday.

The full hydrologic outlook is available through the National Weather Service at weather.gov. Conditions will be updated as the storm system develops.