Despite a dry start to winter, the month of January delivered significant gains for snowfall in the Flathead River basin, with every snowpack telemetry (SNOTEL) site in the Mission and Swan mountain ranges experiencing monthly snow-water equivalent totals in the top three of all years recorded, and most reporting the second-highest or highest totals on record for January.
In most cases, the snowpack doubled and even tripled during the month as abundant moisture spilled into the Treasure State from the Pacific, boosting snowpack in all river basins to near or above normal levels moving into February, according to Lucas Zukiewicz, water supply specialist for the U.S. Department of Agriculture’s Natural Resources Conservation Service in Montana.
“November and December were particularly dry, resulting in snowpack totals on Jan. 1 that were well below normal in the river basins west of the Continental Divide,” Zukiewicz said. “The near continuous snowfall and moisture during January was extraordinary, and it helped the river basins to bounce back to near or above normal for snowpack on Feb 1. It was quite the month.”
On Jan. 1, the high-elevation North Fork Jocko SNOTEL site in the southern Mission Range reported 14.8 inches of snow-water equivalent (SWE), which was 84% of normal for that date.
Between Dec. 30 and Feb 1, however, the site would receive over 18.2 inches of SWE, boosting the site to 114% of normal on Feb. 1, and more than doubling the water contained within the snowpack. Snowpack in the Mission and Swan ranges was near to above normal at all locations as of Feb. 1. Only one region, the lower elevation Salish Mountains west of Kalispell, had snowpack below normal on Feb 1.
The abundant moisture would also help to put a dent in early deficits in water-year precipitation, with most mountain locations recovering to near normal by the time of Zukiewicz’s monthly report.
In some locations, the amount of water added to the snowpack was record setting. Between Dec. 30 and Feb. 1, SNOTEL sites west of the Continental Divide received up to 18 inches of snow water equivalent, roughly proportionate to between 100 and 150 inches of snowfall. Five SNOTEL sites would go on to set new records for monthly totals, and four SNOTEL sites reported their second highest on record.
Snowfall was not as abundant east of the Continental Divide, but Zukiewicz said snowpack improved at most sites.
“Although snowfall wasn’t record-setting in river basins east of the Divide, it was near to above normal for the month, helping the snowpack to improve in most areas,” Zukiewicz said.
The Kootenai River Basin also made dramatic gains in January, rising from well below normal to above normal for snowpack. Two sites outside of Eureka set new records for SWE gain during the month, both at the low-elevation Grave Creek SNOTEL site and the high-elevation Stahl Peak site, which received over 15.1 inches of SWE between Dec. 30 and Feb. 1.
Southwest Montana experienced some of the most dramatic increases with the Jefferson and Madison River basins improving from below normal to near normal for snowpack on Feb. 1. The West Yellowstone area, where mountain snowpack feeds the reservoirs supplying water to the Madison River, was well below normal on Jan. 1.
“The mountains above Hebgen Lake received significant snowfall this month, helping to not only improve conditions for winter recreation, but water supply prospects this spring and summer,” Zukiewicz said.
South-central mountain ranges experienced slight increases in snowpack percentages during the month, while north central mountain ranges had a slight decrease from well above normal.
“This region had been benefitting from early October snowpack which remained on the ground, keeping snowpack totals near to slightly above normal on Jan. 1, and it remains there at this time,” according to Zukiewicz.
At this point in the winter, around 60% to 70% of the seasonal peak snowpack has typically accumulated in river basins west of the Divide, while 55% to 65% of the seasonal peak snowpack has accumulated east of the Divide.
“The coming months will tell us just how full the mountain snowpack reservoir is before spring runoff, and early February looks favorable for continued snowfall,” Zukiewicz said. “Hopefully this wet pattern persists, and we can put some more water in the bank.”