A full slope collapse and a D1 natural wind slab avalanche on Lincoln Ridge.

We toured on Lincoln Ridge today to examine what effect if any the rain in this elevation zone on Dec 3 had on the Dec 1 faceted PWL. The answer is, not much. Rain did not percolate down to the depth of the facet layer. At 7,500' the rain crust was 2 cm (1 inch) thick. There was still 40 cm (16 inches) of recent storm snow between the rain crust at the Dec 1 PWL that had not been affected by rain. At this location, stepping off of skis to dig a snowpit triggered a slope scale collapse with a loud whumpf. No cracking was observed and no avalanches occurred in the steeper adjacent terrain that we were well away and protected from. Lower down at 6,800' the rain crust was 5 cm (2 inches) thick and had no PWL below it in the location we looked.

Along the ridgetop we observed the crown of one very small (size D1) natural avalanche. The crown height of less than 1 foot coincided with a shallow weakness we observed within the most recent storm snow.

Cornices building out in near treeline terrain were weak and collapsed easily.

We experienced continual snowfall in this area today from 10 am to 2 pm with accumulation rates ranging from 0.5 to 2 inches per hour (S1 to S4).