BOZEMAN, Mont., January 9, 2015—Mountain snowpack has made dramatic improvements across most of the state since the end of November. Snowpack began accumulating in the mountains a few weeks later than normal this water year, but two storms at the end of November and December raised most basins in the state from well below normal snowpack conditions in mid-November to above normal on January 1.
Across the state, most basins are near normal to well above normal for January 1. The Kootenai River basin and Lower Clark Fork River basin, both west of the Continental Divide, were below normal. East of the Divide, the Madison River basin and the St. Mary-Milk basin were below normal. Throughout the state, snowpack is currently 109 percent of normal for January 1 and 99 percent of last year at this time.
Normally at this time of year, Montana's snowpack is at 40 to 45 percent of the state's annual peak snowpack for the year. With so much of the winter left to come, streamflow prospects in the spring will be influenced by the weather and snowfall over the next five months.
East of the Divide, southern Montana basins were well below average for fall precipitation during October. Basins west of the Divide were near to above average. With the change in weather patterns in late November, snowfall precipitation at SNOTEL sites across the state resulted in above average conditions by the end of November.
Because of the snowfall in late December, the water year-to-date (beginning Oct. 1) average precipitation statewide for January 1 is 112 percent of normal, 132 percent of last year at this time. Currently, the Madison River basin is the only major basin in southwest Montana that is below normal for the water year. The Ruby and Red Rocks area, located in the headwaters of the Jefferson River basin, are also well below normal for January 1.
Streamflow forecasts could change significantly before runoff begins in April or May, due to the uncertainty remaining about the amount of snow that will fall. Based on January 1 data from SNOTEL and snowcourses across the state, streamflow forecasts are slightly above average statewide at 107 percent of normal and 78 percent of last year for the April through July time period. Currently, some basins in southwest Montana have below average streamflow prospects based on January 1 data. However, there is a lot of winter left to help improve these numbers.
Posted by Jami Howell