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Wet April Boosts Northwest Montana Snowpack, Still Below Rest of State

With stage set for runoff, summer streamflow forecasts for Flathead and Kootenai River basins among lowest in Montana

By Myers Reece
Spruce Park along the Middle Fork Flathead River in the Great Bear Wilderness. Beacon File Photo

Erratic winter weather has continued into spring, with above-average precipitation in April coming on the heels of a record-dry March and bumping up snowpack levels in many areas across Montana, including the Flathead Valley, according to the most recent water supply outlook report from the U.S. Department of Agriculture Natural Resources Conservation Service (NRCS).

Still, as was the case all winter, Northwest Montana has the lowest snowpack in the state, even as the high-mountain snowfall in April increased the Flathead River Basin’s snow water-equivalent to 92 percent of normal as of May 6. The Kootenai River Basin’s snowpack is the lowest in Montana at 85 percent.

All of that translates to the Kootenai and Flathead River basins having among the lowest summer streamflow forecasts in Montana at 81 and 87 percent of average as of May 1, respectively, while other basins in the state show near or above average stream volume forecasts.

Even as low-elevation snow was melting in April, snowpack was building in the higher elevations and adding water contained within the snow, while rainfall was dampening the valley floors. The NRCS says “an active storm pattern delivered most of this month’s precipitation during the first three weeks of April, falling as both rain and snow in mountain and valley locations.”

“Some monitoring sites in valleys and mountains of the Bitterroot, Madison, Gallatin, and Upper Yellowstone River basins just experienced the ‘wettest’ April on record,” Lucas Zukiewicz, who measures snowpack and makes streamflow forecasts for the NRCS, said on May 6.

Low-elevation melting contributed to high early-season streamflows, while higher elevations are primed for melt-off this month, which will lead to continued runoff in creeks and rivers. However, northern river basins, including in Northwest Montana, “have long-running deficits in precipitation totals going back to last summer,” the NRCS says, and “may receive below normal volumes of water this runoff season.”

“A wet May and June could help to offset the deficits in snowpack and water-year precipitation we have in some areas,” Zukiewicz said, “but given the uncertainty in the weather patterns this winter and spring it’s a guessing game as to what will actually happen.”

The NRCS also notes that snowpack is only one of various factors in seasonal runoff, with others including spring and summer precipitation and temperature.

“When looking at forecasts, consider that there are multiple outcomes from this point in time and that future weather will dictate the total amount of water in the rivers this year,” the NRCS states.