Bitterroot Snowpack Feels the Heat
The heat of April took the mountain snowpack down and caused some early flooding in the Bitterroot Valley.
The monthly snow survey of the Natural Resources Conservation Service shows that after the two-week heatwave, the Bitterroot River basin snowpack is now 84 percent of average, which is a 22 percent change from the month before. The lower level snowcourses have melted out.
Brian Domonkos, Montana NRCS water supply specialist, said most of the automated SNOTEL sites “reached their maximum snow water equivalent during the first two weeks of April.”
The last two weeks of April caused the melting. National Weather Service officials issued flood warnings and advisories throughout the valley, and the river gauge at Bell Crossing peaked just above flood stage April 27th, then went back down. At Painted Rocks Reservoir in the south end of the valley, water went over the spillway on April 24, which is one of the earlier “spills” on record.
The Pacific Ocean weather pattern La Nina has faded and no major pattern has yet replaced it, so long-range forecasting is difficult, according to Missoula weather forecasters.
Meanwhile, Domonkos of the NRCS said that rivers usually peak in May, and, of course, warmer weather could move the peak flows above average.
With normal temperature ranges, it looks like the streamflow of the Bitterroot River from May to July will be 95 percent of average.
Other parts of the state are not faring as well, with streamflows as low at 55 percent of average on the Jefferson and 72 percent on the lower Yellowstone.