CODOS UPDATE MAy 30: Snowmelt As We head into June
Greetings from Silverton,
June is upon us and we are into the last few weeks of the bulk of snowmelt. Many stream gauges recently have shown their third leveling off, or sideways movement of spring due to recent general inclement weather (although many are well above median flows). Here in our study basin at Red Mt Pass our historical data indicates to expect the first streamflow peak around June 8 for some adjacent watersheds and the second peak a few days after. There is still snow to melt, at Swamp Angel we observed 15.9” SWE two days ago, current depth is 24”. At Senator Beck current SWE estimation is 17”, current depth is 35”. Between May 22-28 we lost SWE at a rate of 1.4”/day. Albedo is tanking, today our data shows 48% at Swamp Angel and 54% at Senator Beck. Previous years indicate once we are in the 40 range it is a rapid race to snow-all-gone.
All that said, how snowmelt and streamflow unfold the next couple weeks could be clearer, the weather looks to muddy the picture a bit. The next couple days we are leaning towards warm and sunnier weather, but after that the long-term forecast is calling for wet conditions extending well into June. This weather pattern of cooler/cloudy/rain/snow may possibly make the typical runoff peaks not so peaky and more subdued. Dust for the season is at the surface, and pretty bad in many regions, but it is still possible to experience albedo resets, where fresh snowfall provides a reflective surface for 1-2 days thereby slowing snowmelt and possibly alter when peak streamflows occur. It is my guess any precipitation will not appreciably change albedo, but we have seen light graupel events in June change albedo and thus the hydrograph in years past.
Here in a couple days we expect to report on observations at the southern CODOS sample sites.
More Soon,
Jeff Derry
Below: WY2017 seems to be the best analog year for some southwest basins, over the past week the snowpack melting has outpaced 2017.
Senator Beck Basin: Plots below show current SWE conditions at Swamp Angel (11,000’). Dust is at the surface and the snow surface is cupping. Still a lot of snow above treeline and around the 11,000’ elevation zone.
