Observation: Mill D North 12/30/2011

Observer Name:

Robbins

Region:

Salt Lake
Big Cottonwood Canyon
Mill D North

Observation Date:

12/30/2011

Location or Route:

Mill D North/Powder Park/Three Bears (yo cowboy, remember this?)

Weather

Weather Comments:

Warm (pools of water in the skin track on the way out), increasing clouds, and increasing W winds throughout the day.

Snow Characteristics

New Snow Depth:

New Snow Density:

High

Snow Surface Conditions:

Powder

Dense Loose

Wind Crust

Snow Characteristic Comments:

About 10 cm dense new snow/new graupel sits on wet facets, which sits on dry facets. Ridges were scoured, with small-ish loading on the lee slopes. Trail breaking and riding conditions were 'challenging' between 7500 and 9000 feet. The damp snow near the surface was not supportable, and your skis/board would easily submarine into the dry facets below. Riding conditions should improve by morning, as the damp snow will have a chance to solidify (and become more supportable) with the cooler overnight temperatures.

Red Flags

Red Flag Comments:

No collapsing or cracking noted, although I'm sure that it was out there. (We didn't venture off previously established skin tracks on the uphill.) No snow was moving on the downhill, even as we skied some lightly wind-loaded areas.

Primary Concern

Primary Concern:

Persistent Slabs

Probability:

Moderate

Aspect:

North

Northeast

East

Northwest

Elevation:

High

Mid

Trend:

Same

Primary Concern Comments:

The extremely loose, faceted snow near the ground escaped this round of warming and light drizzle. Now, we're set up to have a more cohesive slab atop that, as the damp faceted snow (maybe 15cm) has a chance to solidify and stiffen with the cooler temperatures overnight. Look for continued collapsing and increasing propagation potential (with the stiffer slab). Tomorrow's avalanches will be a little harder to trigger, yet bigger (i.e. wider, not deeper).

Quick handpits on the up showed easy shears below the new snow/old snow interface. This was especially noticeable in areas where the damp snow has had a chance to set up into some sort of crust (with the shears occurring just underneath the crust).

snow_profile_location:

Observed Danger Rating:

Moderate

Forecast Danger Rating:

Moderate