Here comes the melt: Rivers, streams rising

A trend of warmer weather will settle in over Western Montana this week and the deep mountain snowpack finally will start to melt, with rivers and streams expected to approach or exceed flood stage by the middle of next week.

The forecast calls for temperatures in the 60s or higher through Saturday, along with a chance of showers and thunderstorms during the latter part of the week.

“We just anticipate the melt to occur,” said Marty Whitmore, warning coordination meteorologist with the National Weather Service in Missoula. “We’re going to see significant rises in creeks and small streams ... Some of those are going to start coming out of their banks.”

Fast-reacting streams flowing out of the Swan and Mission mountains, as well as those flowing out of the Cabinet Mountains near Libby, are considered likely to flood. Because those streams don’t have automated flow gauges, Whitmore said the National Weather Service is counting on the public to report flood activity on small streams.

The Swan River downstream from Swan Lake is expected to reach 6.7 to 7.4 feet, exceeding its flood stage of 6.5 feet.

“That could be the highest crest we’ve seen” on the river, Whitmore said. The previous high was 7.34 feet in 1974.

Whitmore warned that if there are well-above-average temperatures over a sustained period, flooding could exceed forecasts for rivers and streams.

Largely because of the delayed snow melt in the Flathead River Basin, snowpack numbers as percentages of long-term averages have been rising. At some snow measuring sites, the water content of the snow is two to three times average — or higher.

Whitmore released the following flood forecasts for other rivers:

• The main Flathead River at Columbia Falls is expected to reach 12 to 12.6 feet. Flood stage is 12 feet.

• The Middle Fork Flathead River at West Glacier is expected to reach 11.1 to 12.1 feet, exceeding its flood stage of 10 feet.

• The Whitefish River is expected to reach 7 to 8 feet. Flood stage is 8.5 feet.

• The Stillwater River is forecasted to reach 7.1 to 7.4 feet. Flood stage is 7.5 feet.

Farther to the west, “The Yaak and Fisher rivers have the best chance to go to flood stage” by next week, Whitmore said.

• The Yaak River at Troy is expected to reach 9.1 to 9.5 feet. Flood stage is 8 feet.

• The Fisher River is expected to reach 7 to 7.7 feet. Flood stage is 7.5 feet.

Reporter Jim Mann may be reached at 758-4407 or by email at jmann@dailyinterlake.com.