As of Tuesday, March 17, 2015
As a region, the Clearwater River Basin remains close to average for precipitation, according to the February statistics from the Natural Resources Conservation Service (NRCS). Statewide, precipitation for the month was about 50-90 percent of average for most of Idaho; the water year-to-date precipitation is 70 to 105 percent of average.
According to NRCS’s water supply outlook report, February precipitation in the Clearwater basin as a whole was below normal at 81 percent. However, strong precipitation numbers from the fall mean the region’s water year-to-date remains near normal at 97 percent of average. Individual basins show moderate variability with the North Fork Clearwater River having 91 percent of average and the Selway River reports 119 percent.
Snowpack in the Clearwater basin as a whole is 74 percent of normal, with a strong north to south (dryer to wetter) trend, resulting in values ranging from a low of 71 percent for the NF Clearwater to a high of 103 percent of normal for the Selway. Those figures are down from last year’s medians of 116 and 148 percent, respectively. The Lochsa River reported 83 percent of normal, down from last year’s 129 percent.
According to NRCS, reductions in the snowpack percentages from the February numbers represent both below average accumulation, as well as unseasonable melting at lower elevation sites.
“This year the jet stream pattern has taken abundant moisture and arctic cold to the central and eastern United States. In Idaho, we’ve seen a larger percent of the moisture falling as rain rather than snow,” said Ron Abramovich, NRCS water supply specialist. “A ‘Snow Drought’ is the best term to explain this year’s unique weather pattern.”
Idaho’s snowpacks varied more at the end of February than they did at the beginning Abramovich said. Pockets of good snow can be found across the state depending on elevation, slope aspect, February temperatures, whether the snowpack was able to absorb February’s rain, and proximity to the jet stream path on the east side of the continental divide.