Record-dry March leaves Montana basins with dwindling snowpack
After getting a huge boost in February, Montana’s snowpack statewide has dwindled to average, while some areas have a deficit once again due to a record-dry March.
Montana’s weather has gone to extremes this year, with record cold and snow in February followed by a record lack of precipitation in March.
All mountain ranges in the state received below-normal snowfall for March, according to the April 1 water supply report issued by the U.S. Natural Resources Conservation Service.
“Many mountain SNOTEL sites received record-low March monthly precipitation totals, and others were second lowest on record,” NRCS water supply specialist Lucas Zukiewicz said in a prepared statement.
Overall, the state received less than half of the precipitation normal for March and has about 25 percent less precipitation than last year. That’s not good for western Montana, which tends to see decreasing precipitation as summer approaches. Storms tend to hang around longer east of the Continental Divide.
The result is that snow in northern Montana is less than the 30-year average, with the Kootenai, Flathead, Sun-Teton-Marias and St. Mary-Milk basins having less than 86 percent of what they should have.
The Bitterroot and upper and lower Clark Fork basins managed to come out of March with about average snow.
The Madison and upper Yellowstone basins did best, with about 115 percent of average snowpack at the end of March.
The April report tends to provide a more accurate prediction of how well Montana’s streams will do in the summer, and some are predicted to be low.
Rivers in regions of the Kootenai, Flathead, the lower Yellowstone in eastern Montana and the Sun-Teton-Marias on the northern Rocky Mountain Front are predicted to have below average flows through the end of July. Rivers in the Kootenai could be only 75 percent of normal, and most rivers in the Flathead basin are predicted to be about 80 percent of normal.
The Clark Fork River above Missoula should have average flows, but will fall off as it flows past St. Regis and Plains. By the time it reaches Thompson Falls, the Clark Fork could be 65 percent of normal due to low water flowing in from the Flathead River.
Due to a little less snow and precipitation than the upper Clark Fork received, the Bitterroot River is predicted to flow at 90 percent of normal this summer.
With long-range forecasts predicting above normal temperatures west of the Divide, conditions could worsen for the Kootenai and Flathead. But winter might not be over yet.
“Snowpack across the state typically peaks during the month of April, meaning the next month will give us an idea of the total volume of water stored in the mountain snowpack ‘reservoir,’ ” Zukiewicz said. “If this winter has taught me anything, it’s to expect the unexpected. We’ll wait and see what April delivers.”