The Willow Creek Pass CODOS snow pit site had long since lost all snowcover by June 3, and the adjacent Snotel had also just recorded ‘snow all gone’.  However, the alpine terrain on Parkview Mountain and other high terrain in the watershed did retain sufficient snowcover to sustain strong flows in Willow Creek (see below).

Willow Creek just a few miles south of Willow Creek Pass.

The characteristic fawn color of dust event D8, from May 11, was apparent on much of the snow surface on this east aspect of Parkview Mountain, interspersed with lingering patches of the Memorial Day weekend clean snowfall.

Streams in the southern (upper) end of North Park were overflowing, hinting at the high runoff being recorded farther north on the USGS North Platte Near Northgate gauge.  

The west facing terrain of the Medicine Bow Mountains adjoining North Park retained considerable snow cover on June 3, with dust-on-snow widely exposed. 

The Willow Creek CODOS site, with Parkview Mountain in the distance

A view looking west from State Highway 125, on the approach to Willow Creek Pass, looking toward Parkview Mountain (12,296’).  Dust layer D8 was completely emerged at the surface of the lowest snow cover but the alpine terrain showed only small patches of exposed dust.

Snowpack ablation and snowmelt runoff was well advanced by May 10, with dust layers D8/D6 merged and just below a layer of recent clean snow undergoing rapid melt.  The entire snowpack was classified as “very wet”, with slush at the surface.  A concentrated sample of merged layers D8-D5 dust was collected and is undergoing chemical and other analyses by USGS.

Dust layer D8, merged with a much weaker D6 layer, was only very thinly covered with effectively transparent snow in the May 10, 2013 snow pit at the Willow Creek Pass CODOS site.  The snowpack surface, including the dust layers, was saturated with free water. Parkview Mountain is in the distance.

Snowcover was essentially gone in the valley bottom, at the Denver Creek Campground, gone on SE and S and W aspects just above the valley floor, and very thin on NE aspects.

Streamflow at the Denver Creek Campground was quite low and apparently has never risen enough to erode snowcover from in-channel high points.

Dust layer D6 was strongly present, buried 3” below the surface.  Clear evidence of a surface melt episode was observed in the snow immediately below D6 and snow temperatures had warmed from a mean of -2.5° C on March 19 to a mean of -0.4° C, effectively isothermal.

Strong winds scoured hay fields along State Hwy 125, between Rand and Walden, depositing snow on the pavement and promptly creating deep slush.  North Park contains extensive snow cover.

Snow profile at the Willow Creek Pass CODOS site.  No dust was discernible in this snowpack, raising hopes that this could be a dust-free season at least in the northern mountains.

The snowpit face has been brushed to reveal a re-frozen melt water "flow finger", with a 4" x 6" crystal card for scale.  Free water from surface melt often establishes preferred, vertical flow paths through underlying layers.  As that free water encounters significant snow density or porosity changes, at layer boundaries, water may move laterally until finding a weakness through which to penetrate into the next layer down.  Or, free water may accumulate and lubricate at a layer boundary over wide areas, weakening layer-to-layer bonding and eventually releasing a wet avalanche.

Our observations of Willow Creek found the stream well below bank full as seen in the photo below. This photo also shows the results of last spring's very intense runoff, moving very large woody debris down the channel and causing significant alterations to the channel bed and banks.

Andrew Temple digs the Willow Creek Pass CODOS snow pit.

Willow Creek Pass CODOS site.

The long-since snow-free Willow Creek Pass CODOS snowpit site on April 9th, 2012 and in the next photo, over a month later in the prior season, on May 17th, 2011, still with an 88 cm (35”) deep snowpack.

Willow Creek Pass CODOS site on May 17th, 2011, still with an 88 cm (35”) deep snowpack. The previous photo shows long-since snow-free Willow Creek Pass CODOS snowpit site a month earlier on April 9th, 2012.

A view of the Willow Creek Pass Snotel site looking south on April 17th, 2008. Although beetle kill may have further reduced the density of this tree cover, some shading of the snow pillow is still reducing the influence of dust on snowmelt rates at this site.