Mirroring a winter-long trend, Northwest Montana continues to record the lowest snowpack in the state, and forecasts for the Flathead and Kootenai river basins are currently calling for below-average streamflow volumes this spring and summer, according to the U.S. Department of Agriculture Natural Resources Conservation Service’s (NRCS) most recent water supply outlook.
Meanwhile, Energy Keepers, Inc., which operates the Se̓liš Ksanka Ql̓ispe̓ Project, formerly Kerr Dam, announced late last month that it began refilling Flathead Lake on March 10, a month ahead of schedule, due to below-average snowpack and water supply forecasts.
Energy Keepers noted that the Northwest River Forecast Center predicts water supply volumes for March and April at 56 percent and 54 percent of normal, respectively, for the Flathead River basin.
“The current operational strategy is to have Flathead Lake in the top foot of its operating range in time for summer recreation,” Energy Keepers stated.
The NRCS water supply outlook shows that on April 1 Flathead and Kootenai basins had snow-water equivalent measurements of 86 and 84 percent of normal, respectively, which rank as third and second lowest in Montana. The lowest is Sun-Teton-Marias at 81 percent.
Seven of the other 14 sub-basins recorded by the NRCS had snowpacks above 100 percent of normal, or average, as of April 1, with others above 90 percent.
Basins across Montana, including Flathead and Kootenai, received a huge snowpack boost with record or near-record snowfall in February following a dry early winter.
But while March may have ushered in a much-welcomed return to warmer temperatures, following the February cold spell, it also meant lower precipitation. The NRCS says all mountain locations experienced “well below normal snowfall for March.”
“Many mountain SNOTEL sites received record-low March monthly precipitation totals, and others were second lowest on record,” Lucas Zukiewicz, NRCS water supply specialist, said.
Despite the dry March, a number of basins were able to keep snowpack totals at near or above average heading into April. Snowpack percentages in the mountains supplying river basins in the central part of the state are near normal, according to the NRCS, while southern basins also reported above normal totals on April 1.
“February was such a big month for snowfall in the central and southern basins that even though they experienced a record dry March, snowpack remains near or above normal for this date,” Zukiewicz said. “It may have saved winter and our spring and summer runoff.”
But Zukiewicz cautioned that not all river basins have been as lucky, including the Flathead and other northern parts of Montana.
“There are areas of concern in the state,” Zukiewicz said. “Snowpack in the northern mountain ranges remains below normal for April 1 and below normal March snowfall certainly didn’t help.”
The NRCS says river basins west of the Continental Divide are typically frontloaded with snowfall and precipitation from November through March, while basins east of the divide typically experience their largest monthly precipitation totals from March through June.
“That means that the time for recovery in snowpack totals before runoff begins in these areas is running out as we progress further into spring, especially in northern basins west of the divide,” Zukiewicz said. “While it’s still not impossible, it is less likely.”
While river basins in northern Montana, including the Flathead and Kootenai, are forecasted to have below-average streamflows this spring and summer, basins in the central and southern parts of the state have forecasts that are near to above average.
Spring snowfall in the mountains and valley precipitation play an important role in the runoff for any given year, the NRCS says, and this year will be no different.
“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. “That will tell us a lot about what we can expect relative to spring and summer runoff.”
Long-range forecasts issued by the National Weather Service’s Climate Prediction Center indicate increased chances of above-average temperatures across the western half of Montana for April through June and increased possibility of precipitation across the southern half of the state.
“If this winter has taught me anything, it’s to expect the unexpected,” Zukiewicz said. “We’ll wait and see what April delivers.”
The NRCS water supply outlooks can be found online at www.nrcs.usda.gov/wps/portal/nrcs/mt/snow/.