Water Supply Outlook Reports - Montana

Snow Surveyors Elena Garcia and Zachary Denison measuring Norris Basin Snow Course in Yellowstone National Park on January 1, 2023. They found 4.4” of snow water equivalent at the snow course, which is above normal for January 1 and similar to conditions across the rest of the region. The snowpack is off to a good start this year and across Montana conditions are currently above normal. The timing of snowpack onset this season was near normal, and precipitation has been consistent since October, however there are still 3 to 4 months left in the snowpack accumulation season. Continued active weather in the months ahead will be necessary to reach normal spring snowpack levels.

Although much of January consisted of sunny days without precipitation, a major winter storm during the last week of the month added to the snowpack while also improving snow conditions for recreationalists. This storm provided some locations in Montana with two to three feet of snow. While this storm was beneficial, most snowpack percentages decreased over the last month. The snowpack currently ranges from below normal in northwestern Montana and the Rocky Mountain Front to above normal in central Montana. With two to three months remaining in the typical snowpack accumulation season, some uncertainty remains in terms of what spring snowmelt will provide for water supply.

Photo of the northern Bridger Range on February 24 when the ridge top wind gusted 40-50 mph as the weather transitioned from cold and snowy to warm and sunny. Similar to January, February ended with a large storm that brought several feet of mountain snow across much of Montana. February however had more consistent precipitation than January and snowpack percentages are currently near to well above normal in most river basins. Exceptions are basins along the far western and northwestern border of Montana, where the snowpack is below normal. With one to two months remaining in the typical snowpack accumulation season, water supply forecasts are now available statewide.

Photo of Montana Snow Survey Hydrologist Colin Kultys surveying Slag-A-Melt Lake Snow Course in the Beaverhead Mountains on March 28, 2023, a region that experienced active weather in March and rebounded from below normal conditions last month. Excluding Northwest Montana and the Rocky Mountain Front, March precipitation was above normal in Montana. Central Montana and Southwest Montana continued to build on an already exceptional snowpack. Peak snowpack season is upon us and much of the snowpack east of the Continental Divide is near or already exceeding normal peak levels. Snowpack conditions across the state are largely above normal, except in the far northwest region of Montana. April 1 streamflow forecasts are now available in the following report.

Warm temperatures during the week of April 10th resulted in significant melt of snowpack below mid-mountain elevations across Montana. The photo above shows the Shields River near Livingston exceeding its banks on April 12th when it reached an estimated peak streamflow of nearly 5000 cfs, which was the second highest peak on record, only behind 1979. The snowpack across all of Montana appears to have peaked for the season. Low elevation mountain snowpack has seen significant melt and many snow survey stations below 6000 ft have melted out. The high elevation mountain snowpack has only begun to melt. While it’s starting to feel like summer, it’s not uncommon to get rain and snow in May in Montana and snowpack conditions could still change. May 1st USDA-NRCS seasonal water supply forecasts are now available in the following report.

Faster than normal snowmelt during May resulted in a decrease in snowpack percentages from last month and the seasonal snowpack at many monitoring stations melted out earlier than normal. The snowpack only remains at the highest elevations across Montana. While much of the seasonal snow has melted, the total volume of snow water equivalent accumulated this year was near to above normal in all but part of northwest Montana and the northern Rocky Mountain Front. Last month’s rapid snowmelt resulted in reduced water supply forecasts for the summer at most stream gages. Given the quick melt, a normal amount of precipitation over the next several months will be necessary to sustain normal streamflows late into the summer.