Montana Public Radio

Rainy Week Sets Stage For Flooding Across Western Montana

May 18, 2020

Widespread heavy rain showers are rolling through Montana Monday evening. They are expected to intensify through the week, meaning rivers and streams will soon be on the rise.

Steady rain and driving rain storms will be the predominant weather throughout the northern Rockies this week, according to National Weather Service-Missoula hydrologist Ray Nicolas.

“I mean, it’s going to be a general soaker all across the area," he said. "I mean, the good news is we won’t have to worry about any brown grass anymore. ”

Impressive rain totals, ranging from a quarter-inch up to a half-inch, were recorded early Monday afternoon in the Clearwater, Bitterroot and Sapphire mountains.

Shower activity is only going to intensify Tuesday and Wednesday. The greatest accumulations — upwards of two additional inches of precip — will fall over North Central Idaho’s Clearwater range and the higher elevations of Glacier National Park.

Those storms, combined with a snowpack that’s set to melt anyway, are raising region-wide concerns of minor flooding. A flood watch is now in effect for the Clark Fork River above Missoula, and Nicolas said it could exceed its minor flood stage of 7.5 feet by late Tuesday or early Wednesday.

“Where that actually ends up is still a little bit in question, but we’re looking at a good healthy rise on the Clark Fork River and that will present some problems in the normal areas that it does, with some street flooding down in that Orchard Homes area," he said.

Orchard Homes is a low-lying neighborhood on Missoula’s west side, and it's prone to frequent spring flooding.

Francis Kredensor, meteorologist with National Weather Service-Great Falls, said a couple of inches of rain this week probably would not lead to significant flooding in north central Montana. If the storm system stalls and dumps 3-4 inches of rain, it's a different story.

“That could then put some of our rivers on our side of the Divide into flood stage, in addition to the small streams and creeks," he said.

Kredensor warned of additional impacts for farmers and ranchers, including flooded fields and washed out dirt roads.

Long-range weather forecasting models suggest the active and rainy weather pattern will continue in the Rockies for at least another 10 days.