Local river levels drop but peak flows ahead

Although most area river levels have dropped, the National Weather Service is maintaining a flood warning for the Whitefish and Stillwater rivers into Saturday and a meteorologist warns that there are more peak flows to come on Northwest Montana waterways.

Missoula-based meteorologist LeeAnn Allegretto said rain over the last two days will keep the Stillwater and Whitefish rivers close to flood stage and they could rise above that stage the next couple days.

She said the rivers are “notoriously slow to respond to this type of precipitation we’ve gotten,” and that’s why the warning is in place for the weekend.

The forecast calls for today to be dry but there will be a return to afternoon showers over the next few days.

Most Northwest Montana rivers, including the North Fork, Middle Fork and main stem Flathead rivers, rose close to flood stage on Wednesday but flows have declined since then.

Allegretto said these are not peak flows for the spring runoff. Because of the persistent water-loaded snowpack, there can be more and higher peak flows in the weeks to come.

“We’re going into the second week of June and we’re still adding snow to that snowpack” in some places, she said. “This is incredible.”

She stressed that many high-elevation snow measuring sites still have record amounts of snow water content.

The Noisy Basin site on the Swan Mountain range, for instance, still has 70 inches of water contained in 134 inches of snow.

Allegretto said the long-term forecast models show another wet weather system similar to the one that swept over Western Montana this week.

River flows are expected to rise and fall “similar to what we’ve seen over the last two weeks,” and potential flood conditions could persist into July.

With a sustained period of warm weather,  rivers could “really ramp up,” she said. “It all depends on the weather.”