Heavy rain, potential flooding forecast for Missoula over next 36 hours

Flowers bloom on Blue Mountain above the Bitterroot River as it flows into the Missoula Valley. The sunny weather will give way later Monday and Tuesday to heavy rain and the potential for small stream flooding. (Martin Kidston/Missoula Current)

A forecast of heavy rain and melting snow at higher elevations prompted the National Weather Service on Monday to issue a flood watch for portions of Missoula and Ravalli counties through Tuesday night.

The advisory, issued early Monday morning, includes small streams and creeks in and around the Missoula and Bitterroot valleys, along with much of southwest Montana.

“It’s been really beautiful so far, but the weather is going to be quickly changing this afternoon,” said Genki Kino, a meteorologist with the NWS in Missoula. “We have that flood watch out for the Missoula and Bitterroot valleys, and much of southwest Montana, along with Lemhi County in Idaho.”

Kino said moderate to heavy rain is expected to develop later Monday, with precipitation totals of 1 to 2 inches possible by Tuesday afternoon. High-elevation snow melt may further increase runoff, with snow levels dropping from 11,000 feet to nearly 7,000 feet by Tuesday morning.

Snow at upper elevations could be heavy.

“It’ll start off with afternoon thunderstorms today and transition to that steady, heavy rain overnight into tomorrow,” said Kino. “Snow levels will be dropping, but that’s more for the southern end of the Bitterroots. We could see a couple inches of snow at 7,000 feet.”

Several area rivers are running at or near flood stage and could rise over the next few days. The Bitterroot River at Missoula could reach the minor flood stage by Wednesday, along with Bell Crossing near Victor.

“Right now, some of the rivers are rising to near-action stage in some areas,” Kino said. “The forecast is to get close to that flood stage.”

Temperatures are forecast to peak at around 58 degrees on Tuesday in Missoula before dipping to 43 degrees Tuesday night.