Low moisture, snowpack means low streams in western Montana
Laura Lundquist
(Missoula Current) The past few days of moisture pulled some parts of Montana out of impending deep drought, but western Montana is still critically dry with low snowpack and low streamflows.
During Thursday’s meeting of the Montana Drought and Water Supply Drought Committee in Helena, agency specialists summarized the water and drought conditions from across the state, some of which ended up being better than a week ago, thanks to the storm system that pushed through the state during the past few days. Whether it’s enough to slip us through the summer will depend on the coming months.
Michael Downey, Montana Department of Natural Resources Conservation Service Drought Program Coordinator, said the storm made him scramble to adjust the drought numbers in his presentation from what they had been at the beginning of the week.
“After a wetter-than-average February and an average March, things got really dry. It was just kind of scattered storms,” Downey said. “What was a little unusual about this storm is it was a statewide storm, (something) we haven’t seen since last October. We needed it, we really needed it.”
We needed it, because in addition to being dry, the winter overall was also warm. Averaged over the past 180 days, the temperatures in almost every part of the state were at least 1 to 2 degrees above average while average temperatures around Glasgow, the Big Hole and the northern Rocky Mountain Front were 5 to 6 degrees warmer.
What has saved the moisture and snowpack in some places has been the cool weather we’ve seen for the past week, Downey said. Then the storm helped. While some locations in the state received several inches of precipitation - some in the form of snow - other places got less than an inch, including western Montana and along the eastern border. It was enough to allow some places in the north-central and northwest parts of the state to recover from a warm, dry April, at least for the time being.
“It’s fair to say this was a potentially season-changing event,” Downey said. “Suddenly, the Flathead Lake region is trending on the wet side. Up in the northwest, up in the Yaak, they got some real good moisture out of this set of storms. The picture changed really dramatically, and this time of year, that’s a really good thing.”
But it will take more than one spring storm to improve soil moisture conditions across the state. The rain and snow moistened the soils of northeastern Montana down to about 4 inches, but after three years of drought, deeper soils are still parched, said Zachary Hoylman, University of Montana assistant state climatologist. And there was no recharge around Missoula, which received only 0.2 inches of rain.
While the storm brought needed moisture to most places, Montana’s mountain snowpack is still below normal, and that has implications for how long streams have water this summer. Eric Larson, U.S. Natural Resources Conservation Service water supply specialist, said the storm also caused him to change his numbers from the water supply report he issued on Tuesday.
But it didn’t change the fact that basins in the state have received less than 85% of their normal precipitation, except for the Bear Paw Mountains and the south-central basins, such as the Upper Yellowstone, which are close to normal.
“Through yesterday morning, water-year precipitation is below normal especially for most of western Montana,” Larson said.
The snowpack in the Upper Clark Fork and Bitterroot basins is about 65% of what it should be. Worst off is the Upper Missouri basin around Helena, which has about half of its normal snowpack. That’s partly because April was so dry.
When Larson looked at specific SNOTEL data sites, seven in western Montana had record-low precipitation amounts as of Wednesday. A SNOTEL site along the North Fork of Elk Creek in Powell County east of Missoula recorded slightly more than 10 inches, 6 inches less than the median. Stuart Mountain north of Missoula received 27 inches, 8 inches less than the median.
Larson looked at May 1 snowpack in past years and found this year compares most closely to 2001, when streamflows from May to September ended up being dangerously low. This year’s streamflow forecast predicts that only streams in the Bighorn River basin will have close to normal flows, assuming normal weather patterns for the next few months. The streams in the Upper Clark Fork and Bitterroot basin would have 60-65% of their normal flows.
However, this year’s snowpack is so low that even if weather patterns were to improve such that they were cooler with more precipitation, the forecast predicts that streams in the Upper Clark Fork and Bitterroot basins would still have only 80% of their normal flow. But that’s not likely to happen. As of Thursday afternoon, the cool air began moving out and temperatures over the weekend are predicted to near 80 degrees Fahrenheit.
Aaron Fiaschetti, U.S. Geological Survey hydrologist, said several rivers in western Montana, including the Blackfoot River and the Middle Fork of the Flathead River, have dipped to below their average flow within the past week. Most rivers peak in early June but some appear to have already hit a peak, although the recent drops in the annual flow graphs could be due to the cool weather slowing the snow melt. But three or four streams have hit all time low flows for May 9.
“If 2001 is the direction we’re headed, it doesn’t look so good. But it’s still too early (to tell) right now, and we can hope and pray for that rain to materialize and that snow to stay in the mountains and have it come out slowly. It’s a low snowpack year, so we’re in kind of that glass-half-empty scenario,” Fiaschetti said.
May and June are when Montana normally gets the most precipitation. While the storm helped, drought could return if no more moisture arrives and the heat moves in, Downey said. Unfortunately, that’s what the 14-day outlook and the three-month drought outlook are predicting. Fortunately, drought conditions across the state at the end of last summer weren’t as bad as in 2021 and 2022 so we’re starting the summer in slightly better shape.
“It’s going to be a hot summer,” Downing said. “My prediction is that we’re going to see drought conditions existing in pockets across the state. We’re not going to see drought removal going into the summer. It’s not going to be 2021, but I do see drought persisting.”
Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.