January 27th – February 2nd: High pressure and lurking instabilities

By Arden Feldman            CBAC Intern

The Elk Mountains remained under a high pressure ridge with dry, mostly clear skies and warming temperatures for the duration of the week. Cool northwesterly flow started the week off cold with strong valley inversions and clear skies. On the morning of January 27th, the temperature was down to -32F in town and -10F up at the Elkton weather station at 11,000 ft. On the 27th, winds at Elkton averaged 12 mph and gusted to 32 mph out of the northwest, transporting last week’s snow into wind slabs on leeward aspects above tree line. Similar winds continued out of the northwest until January 31st, but temperatures increased over that time. On the 31st, Elkton recorded a high of 33F and a low of 23F, while down in town there was a high of 40F and a low of -8F. These warm temperatures formed stout melt-freeze crusts on southerly aspects over the week. Flow changed to the southwest later in the week, and winds continued but were running low on snow available for transport.

1/30/17 – Satellite image showing relatively clear skies over Colorado.

 

Avalanche instabilities slowly stabilized over the week. Wind slabs and persistent slabs were the primary concerns. Wind slabs formed on leeward aspects during the northwest winds in the beginning of the week. Observers reported a handful of natural wind slabs running on steep, windloaded terrain at higher elevations. On the 1st, an experienced backcountry skier was caught, carried, and sustained multiple injuries after being washed over several cliffs and trees by a relatively small wind slab in consequential, westerly facing terrain above Copper Creek near Gothic

1/27/17 – Natural D1 wind slab that was possibly cornice triggered.

 

1/31/17 – Natural D1 wind slab.

 

1/30/17 – Remotely triggered D1 wind slab.

 

The 1/19 surface hoar continued to plague our area, with reactive persistent slabs up to several feet thick. They became harder to trigger as the week progressed, but they still lurked and avalanches on this layer were triggered almost every day of the week in either our zone or the neighboring Aspen zone. Northerly and easterly aspects near and below tree line were the most suspect slopes to contain the dangerous surface hoar layer.

1/27/17 – Explosive triggered D2 persistent slab.

 

1/28/17 – Snowmobile triggered D1 avalanche that ran across Kebler Pass Road.

 

1/31/17 – Natural D2 persistent slab avalanche that likely ran at the end of the last storm cycle.

 

1/30/17 – Avalanche rose showing persistent slab avalanche activity since January 19th.

 

1/28/17 – CBAC Snodgrass Snow Study Plot profile showing the problematic surface hoar layer.