Snowpack remains mostly near normal after mix of March weather conditions
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News from Natural Resources Conservation Service
BOZEMAN — March brought a combination of snow accumulation, snowmelt, and rain to Montana. “The good news is precipitation was above normal across a majority of the state during March, with nearly all river basins receiving 110-140% of median total monthly precipitation,” said Eric Larson, USDA Natural Resources Conservation Service (NRCS) Hydrologist. The timing and severity of the storms varied across the month. During the first two weeks of March most SNOTEL sites picked up an inch or two of precipitation, however northwest Montana reported slightly more, about 2-4 inches. Storms intensified during the second half of the month and most SNOTEL sites reported 2-5 inches of additional precipitation. Total monthly precipitation ranged from about one inch at several SNOTEL sites in southwest Montana to about 14 inches at the highest elevations in northwest Montana.
“The switch in weather that occurred in late December has improved moisture levels significantly across most of the state, yet deficits persist in a couple locations,” said Larson. Precipitation since October 1 has only been 70-80% in the Sun-Teton-Marias and St. Mary River basins. Upper elevation snow measurement stations in that region had snow water equivalent values 3-8 inches less than median on April 1, which is approximately 65-75% of median. “The Rocky Mountain Front needs several large winter storms during April and May,” said Larson. Other locations trailing behind are the Upper Clark Fork and Powder River which have a 75-85% of normal snowpack. All other river basins have a near normal snowpack 90-110%, except the Smith-Judith-Musselshell which is at 115%. One location in central Montana worth noting is the Big Snowy Mountains where Crystal Lake SNOTEL (6,130 ft) had its fourth highest April 1 snowpack in 47 years, only lower than 2006, 2011, and 2014.
While spring has arrived and recent warm and sunny weather has been a reminder that summer is around the corner, keep in mind that additional snow is needed in mountains. Montana’s mountain snowpack is the primary source of water supply while weather is drier during the summer months, and normal peak snowpack levels have not been reached yet. The only exception is central Montana. “May 1 snowpack conditions will provide a more certain indication of what the snowmelt season will bring and at this point additional precipitation during April should be welcomed,” said Larson. April 1 NRCS Water Supply Forecasts are now published, and they trend with water year precipitation and the ensuing snowpack. Most April-July streamflows across the state are forecasted to be near to below normal at 80-105% of median. Regions with larger water year precipitation and snowpack deficits such as the St. Mary, Sun-Teton-Marias, and Powder River basins are predicting below normal streamflow of 60-90% of median. “Montana’s mountain snowpack conditions are better that last year at this time but, we are not out of the woods yet. Spring is generally a wet time of the year in Montana, hopefully that holds true this year,” said Larson.
A full report of conditions on April 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.
