March brought more moisture, but Flathead basin still at deficit
The Flathead River tumbles down the canyon below SKQ Dam. Streamflow projections across Montana are at or below normal, with forecasters saying more moisture is needed to boost the irrigation outlook. (Kristi Niemeyer/Leader)
March brought a combination of snow accumulation, snowmelt and rain to Montana. The Flathead Basin received 130% normal precipitation in March, although it remains below median at 89% for the water year that began in October.
“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, from two to four inches.
Storms intensified during the second half of the month and most SNOTEL sites reported up to five 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 Oct. 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 that were three-to-eight inches less than median on April 1, or 65-75%.
“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 basins, which have 75-85% of normal snowpack. All other river basins have a near normal snowpack of 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 is a reminder that summer is around the corner, Larson notes that additional snow is needed in the mountains. Montana’s mountain snowpack is the primary source of water supply during drier summer months, and normal peak snowpack levels have not been reached yet.
Monthly temperatures in the western part of the state during March were 3-6 degrees above normal in most areas, which can influence snowpack across the region – especially at lower elevations where widespread melt has already occurred.
Most April-July streamflows across the state are forecasted to be near-to-below normal at 80-105% of median. Regions with larger 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 than 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.