Below normal water supply forecasted for Montana after low-snow winter

Montana’s winter is shaping up to have been among the worst for snowpack in 25 years and, combined with current outlooks, has water forecasters warning that streamflow levels this summer could be well below normal across most of the state.

Early last month, Montana forecasters and water supply specialists said the state would need above-average snow during March and early April, and a wet and cool spring, to keep the meager snow left from melting away too quickly and causing low river and streamflows through the growing season and likely drought.

But according to state and federal reports and presentations released during the past two weeks, the recovery the snowpack made in February and early March tapered off in the weeks since and hasn’t continued to the extent forecasters hoped.

“It’s not likely a full recovery to normal snowpack conditions will occur by May 1 this year across most of Montana,” Montana Snow Survey staff wrote in the April water supply forecast issued by the Natural Resources Conservation Service earlier this month.

“Below normal snowpack conditions on May 1 could be supplemented by above normal spring and summer precipitation, assuming snowpack deficits aren’t too large. Best case scenario would be a return to cooler weather and above normal precipitation for the next months.”

Since 1991, the median day that Montana’s snowpack as a whole reached its peak is April 14, at 18 inches of snow water equivalent, which is the amount of water contained in the snowpack. So far this year, the statewide snowpack peaked at 13.2 inches of snow water equivalent on April 11, three days earlier than normal and nearly 5 inches of snow water equivalent below normal.

The current snowpack of 12 inches of snow water equivalent statewide is just 74% of normal for this time of year, but also in the 7th percentile when compared to 1991-2020. To start the month, one in seven snow monitoring stations in Montana was showing its lowest or second-lowest snowpack on record. More than one-third of them were reporting a snowpack in the 10th percentile or less compared to 1991-2020.

It’s still possible that storms and cooler weather over the next couple of weeks buoy the snowpack at higher elevations and inhibit the melt-off, but this is typically the time of the year the snowpack starts what most people hope will be a gradual decline.

Last year, the snowpack peaked at 18.1 inches of snow water equivalent on April 25, but a quick melt-off ensued because of unseasonably warm temperatures. Two weeks later, the snowpack was at 12.5 inches of snow water equivalent, and it was completely gone by June 21. The median snow-free date is June 28.

As of Monday, the snowpack was gone in the Bear Paw basin. It sat at 45% of median in the Upper Missouri Basin and between 50% and 69% of normal in the Sun-Teton-Marias, Upper Clark Fork, Bitterroot, Smith-Judith-Musselshell, Upper Yellowstone, Gallatin, Lower Clark Fork, and Flathead basins.

The Jefferson (70%), St. Mary and Kootenai (75% respectively), Madison (76%), Tongue (77%), Powder (78%), and Bighorn (85%) basins were all between 70% and 90% of their average snowpack for this time of the year on Monday.

Last week, Dr. Dennis Todey, director of the Midwest Climate Hub for the U.S. Department of Agriculture, said the Upper Missouri River was running at close to its lowest point above Fort Peck in recent decades, which could have ramifications as the river heads east into the Upper Midwest, which just had one of its driest and warmest winters in 100 years.

On the other side of the state, the U.S. Army Corps of Engineers agreed earlier this month to approve a request from the Confederated Salish and Kootenai Tribes’ Energy Keepers, Inc., to raise Flathead Lake’s spring level by two feet to 2,885 feet and hold more water in the lake.

Energy Keepers said it anticipates 2024 will be similar to the record-low flows seen in 2023 that kicked off a political firestorm surrounding the lake’s levels so it started refilling the lake early and believes the lake will be between 2,888 feet and 2,891 feet by the end of May.

“By taking these actions early in the season we increase the likelihood Flathead Lake will reach its maximum elevation in what forecasters are predicting as another dry year,” said Energy Keepers CEO Brian Lipscomb. “Should we experience unforeseen precipitation then we can make further adjustments. By May, we are prepared to make further changes to standard operations depending on weather conditions.”

Most streamflows are forecast to be between 70% and 85% of normal across all of Montana’s river basins, but could be near normal in parts of northwest, southwest, and southern Montana that saw a better snowpack this year.

But rivers including the Bighole, Blackfoot, Little Bighorn, Tongue, Clark Fork, Smith, Sun, and Teton are expected to see streamflows for April through July below 65% of normal, according to the latest forecasts.

Those streamflows will be critical to recreation and especially agricultural production this summer, and the relatively dry winter has led to an overall expansion of drought since the beginning of the year, as the area of the state experiencing moderate and severe drought has more than doubled.

But drought conditions improved in Montana throughout March and into the beginning of April. During the past two weeks, moderate and severe drought has declined in southeastern Montana, and less of east-central Montana is abnormally dry than a week before. But after extreme drought disappeared for a week earlier this month, it has shown back up in northern Flathead County and northwestern Mineral County.

“Extreme drought conditions were introduced in the mountainous region along the Idaho and Montana border due to concerns about low snow amounts and possible early snowmelt,” National Drought Mitigation Center forecasters wrote in last Thursday’s report.

The next two weeks could bring some relief if current forecasts hold. The Climate Prediction Center is forecasting above-average precipitation over the next 6-14 days, including a possible storm this weekend that could bring rain to lower elevations and snow above 5,500 feet, according to the National Weather Service.

But the forecast for early May currently shows above-average temperatures statewide, and the forecast for May through July shows above-average temperatures and below-average precipitation for western Montana, though it also shows equal chances of below- or above-average precipitation and temperatures for eastern Montana for that period.

That will coincide with the El Niño that has persisted through winter ending, and an increasing likelihood that La Niña starts to develop into August, according to the Climate Prediction Center, which typically means cooler and wetter winters in Montana because the jet stream stays further north.

But July through October are currently forecast to bring above-normal temperatures and below-normal precipitation for Montana, according to the Climate Prediction Center. That means the next several weeks will be key in determining how summer shapes up water-wise.

“Given the widespread low forecasts, above normal precipitation over the next couple of months and a slow melt of the snowpack would be most beneficial for the upcoming summer,” the latest water supply forecast says. “Additionally, a wet summer could help to sustain streamflows later in the season.”