Rivers and streams are running high across the state of Montana from May snowmelt, and most have been above average for daily streamflows throughout the month. Data from the USDA Natural Resources Conservation Service showed that snowpack at high elevations in most basins peaked during the first week of May, but saw a rapid transition to melt shortly afterwards.
“The high pressure which dominated the weather patterns this month brought abundant sunshine, mostly dry conditions, and above average temperatures—the perfect combination for snowmelt,” said Lucas Zukiewicz, NRCS water supply specialist.
Some snow did fall in the high country over the month, adding to snowpack totals. SNOTEL (SNOwpack TELemetry) sites along and east of the Divide were treated to up to 31 inches of snow on May 18, providing one last day of powder skiing for those that were motivated to hike for it, Zukiewicz said. More importantly, he said this storm also helped to slow the snowmelt which was occurring a little quicker than normal due to the persistent warm and sunny weather.
Peak snow accumulation was above normal in many basins in the state, although a few central basins were below normal throughout the year with regards to snowpack. On June 1 many basins have snowpack in place that remains near to above normal for this date, but it has been melting faster than normal.
“To some extent, the above normal snowpack totals this year have been able to offset the rapid melt rates experienced during the month of May, leaving us near to above normal for today, but continued sunny and warm weather could move what’s left in the hills faster than we’d like to see it come out.” Zukiewicz explained prolonged snowmelt is beneficial in many ways. It helps to keep water in the rivers later into the summer, keeps river temperatures down, and keeps water available to the irrigators in the state when demand is high.
Some basins that feed Montana from the south experienced record snowpack, causing concern over how much water would enter the rivers and reservoirs, and just how quickly the snowpack would melt out. “So far what has happened has been ideal,” Zukiewicz said. “The snowmelt spigot has been turned on and off a few times this month due to the periods of cooler weather, releasing the water in phases instead of one big push.”
With snowpack well above normal, there is still a large volume of water waiting to melt in the mountains of the Wind and Shoshone River basins. Federal and State water managers have worked diligently to plan for and manage the anticipated river flows, Zukiewicz said.
Long duration seasonal volume forecasts issued by the NRCS on June 1 indicate near to above average streamflows for the June-September period in many locations, but vary by basin. However, the weather over the next few weeks will play a critical role in the timing and magnitudes of flows in the rivers across the state of Montana through the summer. “Everyone is ready to get out and enjoy the mountains of the state, but cool and wet weather, and keeping the snow up in the hills as long as we can, will be better in the long run,” Zukiewicz said.
Monthly Water Supply Outlook Reports can be found here after the 5th business day of the month:http://www.nrcs.usda.gov/wps/portal/nrcs/main/mt/snow/waterproducts/basin/