Streamflow forecasts decline as snow melts

The Flathead River’s high-elevation snowpack is melting earlier than normal, causing forecasters to decrease streamflow predictions for the rest of the year.

The federal Natural Resources Conservation Service released its snowpack levels through the end of April on Wednesday, with the Flathead and Kootenai river basins down to 69 percent and 42 percent, respectively, of their average mountain snowpack.

That’s a slight decrease from last month, and the result has been that predicted streamflows for the two rivers have also dropped.

The average streamflow for the Flathead River through the end of July is predicted to be 87 percent of the average. That prediction is 80 percent for the Kootenai River.

However, because snowpack levels are so low, the actual flows through the end of the summer will be more variable and dependent on precipitation levels, according to conservation service hydrologist Lucas Zukiewicz.

“That [snowpack] is going to come out a lot quicker than it normally would, so we’re going to be a lot more reliant on precipitation during the summer to keep water in the streams,” he said.

At the beginning of April, temperatures were low enough at elevations above 6,000 feet that most of the snowpack was staying put, but high-elevations snows began melting more quickly than usual last month. By mid-April, snow at all elevations had begun to make that transition.

Compared with the rest of the state and most of the West, Northwest Montana has been in good shape this year, having benefited from heavy snow events early in winter and additional snowfalls in the high elevations during February and March.

But that trend started to turn around in April, and Zukiewicz said the mountains got about half their normal precipitation for the month.

According to the National Weather Service office in Missoula, Kalispell registered 0.35 inches of precipitation in April well below the average of 1.24 inches.

“We did see the persistence of this warm, dry weather pattern that we’ve had. It might have been one of the first months west of the Divide that you’ve been getting what most of the state has been getting,” Zukiewicz noted. “But people that live in that area are still fairly fortunate — those are some of the highest stream flows in the state.”

Elsewhere in Montana, this summer is shaping up to be an even drier one. The Missouri River’s predicted streamflow is 47 percent of the average, and the Yellowstone River is at 67 percent. Statewide, rivers and streams are forecast to run at 69 percent of the norm.

Reporter Samuel Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com