Montana water supply outlook
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News from NRCS, USDA
Following an exceptionally slow start to the water year, winter weather arrived in February and provided much needed precipitation to the region. Precipitation last month was above normal in all but the northern Bighorn Mountains. Snowpack percentages have increased in all basins, but overall, the snowpack remains below normal. The recent improvements were timely, but there are only one to two months remaining in the normal snow accumulation season and more snow is needed.
On Jan.1, the snowpack at about 110 of 175 NRCS snow monitoring stations reported their lowest or second lowest snowpack on record in Montana. On March 1, less than 60 of 230 stations reported their lowest or second lowest snowpack on record. March 1 snowpack numbers used in this report are calculated from March 1 SNOTEL data (00:00) and data from manually measured snow course surveys that are conducted the last week of February. Since the time that most of those measurements were conducted, a winter storm swept across western Montana. The snowpack has improved from this early March storm, but only put a dent in the large upper elevation snowpack deficits.
Water Supply forecasts are published in the March 1 through June 1 Water Supply Outlook Reports. Given the overall below normal snowpack on March 1, streamflows are expected to be below normal for the April-July and April-September periods. With one to two months remaining in the normal snowpack accumulation season, continued active weather will be needed to make further gains on the snowpack deficit.
The following chart displays the exceptional improvement in snowpack conditions in the mountains surrounding Helena. From early December to mid-February the basin wide snowpack was the lowest on record. Substantial precipitation during February significantly improved the snowpack conditions, but more snow is needed.
Flathead
Precipitation in February was above normal at 116%, which brings the seasonal accumulation (October-February) to 83% of median. The snowpack in the Flathead is well below normal at 72% of median, compared to 94% at this time last year.
