April Storms Delay Snowmelt, but Fail to Recover Snowpack Deficits

Photo caption: Each month, snow surveyors ascend from the valleys to manually measure snowpack at over 100 snow courses across Montana's watersheds. The data from these snow courses supplements the data from SNOTEL sites to help produce the monthly water supply forecasts. In the pictures, surveyors navigate the tricky access to Mudd Lake Snow Course in the Anaconda-Pintler Range and experience conditions that defined the winter of 2026. Dirt up to 7,000 feet in the Big Hole Valley meant carrying skis for the first portion of the survey. At 7,360 feet, the snow course measured 44" of snow and 15.9" of snow water equivalent, or 82% of median for its 39 years of observations. December, January, February and March brought higher than normal temperatures resulting in a stubbornly high snow line. Photos: L - Joe Kral, NRCS hydrologist. R - Javier Colton, NRCS hydrologist. April 28, 2026

While snowpack conditions across much of the western United States remains uniformly poor, the snowpack across Montana watersheds paints a more nuanced picture.

Warm temperatures and variable precipitation defined the winter of 2026. As a result, the snowpack conditions varied greatly across aspect and elevation. April brought near normal monthly average temperatures to Montana for the first time this snowpack accumulation season along with near to above normal precipitation across the state. While April storms stalled snowmelt they fell short of meaningfully improving snowpack conditions. As of May 1, snowpack statewide ranged from 40% to 100% of median. In such a spatially variable year, looking at smaller watersheds as opposed to major basins provides a more accurate picture. Regions that benefitted the most from spring storms such as the Missoula area, Flint Creek, Swan Valley, and Blackfoot have near normal snowpack. Higher elevations in the Beartooths report near normal snowpack as well. The rest of the state has well below normal snowpack at 40% to 85% of normal. The Bighorn, Powder and Tongue basins have 25% to 60% of normal snowpack, with the Powder and Tongue basins recording their lowest years on record.

"When assessing the volume of water stored in the snowpack, peak snowpack is a good indicator of how full the snowpack reservoir was filled this year," explains Florence Miller, USDA Natural Resources Conservation Service Hydrologist. "Peak snowpack is the highest snow water equivalent (SWE) measured at a given site during the winter. In Montana, SNOTEL snow monitoring sites typically peak between 5 and 45 inches of SWE, depending on region and elevation. This year, most sites recorded substantial peak snowpack deficits ranging from 1 to 14 inches below normal. Thirty-one SNOTELs measured their lowest peak snowpack values on record. A few higher elevation sites were the exception, showing surpluses of 3 to 10 inches of SWE."

In addition to causing significant spatial variability in snowpack distribution, the warm winter also led to accelerated snowmelt. Most SNOTELs reached peak snowpack accumulation, and transitioned into snowmelt, several weeks earlier than usual. Thirty-two SNOTELs recorded their earliest melt out date on record. This premature snowmelt triggered early runoff, and many watersheds across the state observed well above normal March and April streamflows.

Drought conditions follow this spatial and temporal variability. Water-year-to-date precipitation totals remain near to above normal, largely carried by the December atmospheric rivers. As a result, soil moisture looks promising across much of northwestern Montana and parts of central and eastern Montana. However, well below normal soil moisture is intensifying in the southwest corner of the state. As a result, 87% of the state is in drought conditions, with drought conditions improving in northwest Montana while extreme drought conditions persist along the Rocky Mountain Front and in southwest Montana.

May 1 NRCS Water Supply Forecasts predict below normal streamflow statewide, though with substantial regional contrasts. At the 50% exceedance probability, higher elevation watersheds in the Absaroka-Beartooths predict close to normal streamflows. Regions favored by spring storms including tributaries of the Upper Clark Fork, Blackfoot, Bitterroot, and drainages of the Swan and Mission Mountain are forecast to see near normal flows. The Flathead River forks predict streamflow of around 80% of normal. East of the divide, most forecast points fall between 70% to 90% of normal. Regions experiencing more severe drought conditions such as the Beaverhead and the Three Forks of the Missouri are projected to have 60 to 75% of median streamflow. Watersheds with large lower elevation plains influence such as the Musselshell, Shields, Tongue, Powder, and Bighorn forecast less than 65% of normal streamflow.

"When looking at streamflow forecasts, it is important to take into account the full forecast suite, not just the 50% exceedance probability forecast," said Miller.

Generally, the 50% exceedance volume is reflective of what streamflow volumes could be under typical spring and summer conditions. The 30% or 10% exceedance forecasts reflect potential streamflow volumes given wetter than normal future weather conditions and the 70% and 90% exceedance forecasts represent expected volumes with drier future weather.

"Spring precipitation and cooler temperatures to slow snowmelt could help improve these forecasts, though in most regions, full recovery to normal streamflows is unlikely. Current predictions of warm temperatures and below normal precipitation could result in more severe streamflow deficits, with rivers reaching well below normal volumes. Additionally, with snowmelt occurring earlier than normal, runoff volumes are likely to be shifted earlier in the season," continues Miller.

More Information

A full report of conditions on May 1 can be found in the monthly Water Supply Outlook Report available on the Montana Snow Survey website. In addition, real-time snow survey data can be found at nrcs.usda.gov/montana/snow-survey.

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