See-saw Weather Makes Montana Streamflow Experts Nervous
The rivers of Montana depend on the winter's snowpack to keep a good streamflow through the summer and fall. Each month, the Natural Resources Conservation Service in Bozeman tries to determine if the water will be available through the year for recreation and for agricultural irrigation. And this year has been difficult.
The February snowpack report was low and below average. However, four weeks later, at the beginning of March. snowpack had rebounded dramatically for a huge gain in the snow levels, especially in the higher elevations.
But then March played some weather tricks on the experts. Water supply specialist Lucas Zukiewicz said, in a news release, "Unfortunately, March weather started off on the opposite trajectory. Warm, dry air spilled into the state during the first week of the month and many mountain (automated) SNOTEL sites matched record daily average temperatures on March 5."
Temperatures remained above average throughout the month. And the snow and rain stopped. Zukiewicz said only the final week of March saw good amounts of snowfall. Many snow courses are still near average for the year, however in the southwestern part of the state, the river basins where were already below normal have further declined. "Forecasts for spring and summer runoff in Montana are the lowest in the Red Rock, Ruby, and Madison river basins," he said.
Looking at our area, the snow pack is 99 percent of normal in the Upper Clark Fork and 95 percent in the lower Clark Fork. The Bitterroot River drainage is at 110 percent of normal, but that dropped 7 percent from a month ago. Precipitation during March in Western Montana was generally only 50 percent of normal. More information is on the NRCS website.
April and May weather will be the key to streamflow this year. Zukiewicz said that historically, April brings more snow to the mountains - both high and mid-elevations, saying, "A return to normal temperatures and wetter weather patterns would be more than welcome at this point to slow the transition of of the mountain snowpack towards melt and satisfy the existing soil moisture deficits present in many valley and plains locations."