Flathead near normal, but many sites report lowest snowpack on record

At the beginning of January more than half of NRCS snow monitoring stations in Montana and surrounding river basins reported their lowest snowpack on record.

“Well above normal precipitation was needed to begin a recovery from lack of snow, yet precipitation was mostly below normal across Montana last month,” said Eric Larson, a water supply specialist with the USDA Natural Resources Conservation Service (NRCS), in a statement released Feb. 5.

The exception was the northern Flathead and Kootenai River basins in Montana where total monthly precipitation was near normal. Other basins west of the Continental Divide received 70-90% of normal precipitation during January.

East of the Continental Divide, the southern Rocky Mountain Front, central Montana, and part of southwest Montana received about 60-70% of normal January precipitation, while Gallatin, Upper Yellowstone, Bighorn, Powder, and Tongue River basins received less than 65% of normal precipitation.

“January began with a promising storm that delivered snow to western Montana,” said Larson. He added that snow depth nearly doubled from about 35 to 70 inches at upper mountain elevations in northwest Montana.

East of the Continental Divide, storm totals during the second week of January delivered about six to 18 inches. That storm was followed by very cold temperatures and relatively inactive weather.

Sixteen SNOTEL sites recorded temperatures below minus 40 degrees and most SNOTEL sites in Montana dipped below minus 30 mid-month. High temperatures on Jan. 12 peaked below zero across much of the state.

Active weather returned during part of the second half of January but was only significant in northwest Montana. Overall, during the second half of January the temperature was well above normal, and precipitation was well below normal for most of the region.

As of Feb. 1, snowpack percentages are still well below normal in all Montana river basins. Currently the Kootenai and northern Flathead River basin snowpack is highest at about 70% of normal. All other basins have a snowpack that is between 40-60% of normal, except for the Upper Missouri and Sun-Teton-Marias snowpack which is between 35-45% of normal.

According to Larson, more than half of NRCS snow monitoring stations measured for Feb. 1 remain at either their lowest or second lowest snowpack on record. Current snow water equivalent deficits range from about 7-10 inches at upper elevations and 3-5 inches at lower mountain elevations across Montana.

“Considering fresh snow falls at roughly 10% density, that’s upwards of 70 to 100 inches of snowfall behind normal in some mountain locations,” said Larson.

With two to three months remaining of the normal season for accumulating snowpack, Larson predicts it’s going to take a major change in weather to rebound from these deficits. But it’s happened before. In recent history, February through April 2003, 2011, 2014, 2017 and 2018 brought precipitation that was well above normal across Montana.

“A three-month repeat like one of those years will be necessary to make gains by May 1,” he said. If precipitation is not above normal over the next several months, streamflows in Montana during the upcoming spring and summer season are likely to be below normal.

Spring and summer water-supply forecasts will be published by the NRCS in the March 1 Water Supply Outlook Report.

A full report of conditions on Feb. 1 can be found in the monthly Water Supply Outlook Report available on the Montana Snow Survey website. In addition, real-time snow survey data can be found at nrcs.usda.gov/montana/snow-survey.