What Happened to Our Mountain Snowpack This Year?
Big winter snow to low summer flow— a tale of two extremes.
From Kerry McClay, National SnowSchool Director (8/4/25)
Did our snowpack melt faster this year? This is a topic I’ve found myself discussing this summer with river runners, backcountry skiers, SnowSchool educators and mountain weather watchers alike.
It seems many people across the West enjoyed average or above-average snow in their local mountains this past winter (a big exception to that is the Southwest). But even with above average snow, the extended spring skiing and strong summer river flows didn’t quite turn out as one might expect. In fact, if you do a quick search of Western river flows right now you’ll find that many are below historical norms (for example, check out early August flows for the Salmon, Snake, Columbia, Upper Missouri,and Roaring Fork rivers).
So what happened?
Climate change? A weak La Nina? Drought? For a deeper dive into the data, I talked with Ron Abramovich, Idaho’s retired NRCS SNOTEL snow guru (who also correctly predicted big snow in the Intermountain West this winter despite forecasts for a “Weak La Nina”).
Abramovich commented, “Well what happened in many places across the west is that the precipitation simply stopped moving in after April 1st.”
“The faucet turned off from April to July.” -Ron Abramovich
Though the phenomenon varies by watershed and geography, across many parts of the West precipitation dropped off dramatically in the spring. You can see the precipitation pattern clearly on this interactive map from Oregon State University that compares monthly precipitation to long-term averages (hint: adjust the month to see April, May and June). And with very few spring snowstorms to keep the snowpack intact, the NRCS SNOTEL map (shown right) illustrates how the mountain snow melted quickly and early.
On April 1st 2025 the NRCS SNOTEL map showed many watershed at or above the historical average. By May 30th the snowpack in most places was well below the historical average.
The Boise National Forest: A Case Study in Vanishing Snow
An example of this rapid transition is clearly observable at places like the Boise National Forest (where our National Flagship SnowSchool Site is located). Here, the Bogus Basin SNOTEL station on April 1st 2025 showed 145% of average snowpack (for that date). And for a big part of late March the station was showing snow-water equivalent levels several inches above the all time observed maximum.
That’s some major March snow! But then quite suddenly all the snowstorms and precipitation stopped. And without spring snow and rain to recharge the snowpack, the warm spring temps quickly sunk snowpack levels down to just 40% of average by May 15th 2025. When the storms stopped coming, the snow didn’t last long!
The US Forest Service and the SnowSchool team at Bogus Basin measuring a big snowpack at the SnowSchool Weather Station in late March. This snow was all but gone by May. Photo credit, WWA.
Curious About Your Watershed? Try This:
If you are interested in zeroing in on the exact pattern for your local watershed and community, this is something you can try on your own in three simple steps:
- Click this link for Interactive Map of snowpack levels on April 1st 2025
- Zoom in on the to your location / community
- Click the SNOTEL station nearest to your location such that the graph of snowpack levels becomes visible (click the graph to see it in a separate tab)
Using this method above, you can find similar patterns (above average winter snowpack followed by a rapid decline) in certain areas of the Wasatch Mountains, the Nevada portion of the Owyhee Mountains, in the Cascade Mountains (near Cater Lake) and up on Niwot Ridge in the Colorado Front Range.
SnowSchool at Aspen Center for Environmental Studies where snowpack in Colorado’s Roaring Fork Watershed was near the historical median in March 2025, but quickly declined in the spring . Photo Credit: Sam Ferguson
Living Through Extremes: The New Normal?
It seems many places across the West experienced a form of precipitation whiplash, with an extremely snowy winter immediately followed by an extremely dry spring. Such extremes are, by definition, unusual and challenge our water resource managers. Abramovich pointed out this phenomenon creates a big headache for streamflow forecasters (and provides further evidence of why accurate data from SNOTEL is so important).
A very snowy winter followed by an exceedingly dry spring combines two statistical rarities and forces scientists to rely on unlikely forecast scenarios. This is because the most important streamflow forecasts for water users are released on April 1st every year and they are made assuming average spring precipitation will follow.
“I’ve never seen something like this in my 30 year career,” -Ron Abramovich
To illustrate the point, he created a case study and statistical breakdown on his own blog showing how river flows on the wild and scenic Selway River dropped down below even the 90% exceedance range. In other words, forecasters had indicated that there was a less than 10% chance of the river flow dropping that low.
“Without spring precipitation and thus far summer rains to bump the rivers back up a bit, many rivers across the West are reaching their low summer baseflow levels earlier than normal.” -Ron Abramovich
As Abramovich pointed out last fall, we are living through a period of wild weather patterns that seem likely to continue. So whether it’s the oscillating ENSO cycle, ongoing snow drought, a changing climate or huge dumps of mountain snow, here at SnowSchool we’ll continue to track the story of our wild snowscapes and help people learn more about their local winter wildlands.
Look for more winter forecasts and snowpack predictions coming your way this fall!
