December 28
Bowman, Yellow Jacket, Alexander Basin, Gobblers Knob(cabin run, main face).
Snow conditions
Recent storm snow had settled to a depth of 4-8". This was capped by a thin layer of riming(not yet crusted). A new layer of drifting-scouring was also occurring, with cracking a few inches deep in wind effected terrain. Cornice lines were also sensitive dropping easily with kicking but, little propagation.
Weather
Partly cloudy in the am, deteriorating as the day progressed to low clouds and poor visibility. Winds increased from the south, gusting to around 30 mph by late afternoon along the upper elevation ridges. A few sputters of snow, accumulating to less than an inch of dense and rimed.
Avalanche activity
Large slide was observed in upper Alexander Basin. Dimensions of about 200 yards wide, descending about a half a mile, encompassing the entire upper bowl, northwest, north and north east. Slide did not take out the northwest facing coming off Wilson peak, nor did it include the east chute, which released several days earlier.
Crown was up to around 8' in places.
The slide ran on both sides of the secondary ridge in the upper bowl, leaving that snow in place.
A graphic from a portion of the crown, showing two wind events and the crust-facet-crust weakness producing the large slide.
No avalanche activity was observed in the cabin run on Gobblers knob, Raymond Glade or Paradise. The slide on the main face of Gobblers was impressive, even in very low visibility. Took out the entire face from Davis gulch to the low angled sub ridge on the west side, running about 2800' vertical, well down the main gully. Another slide was observed in the Raymond rock slabs bowl, dimensions unknown. Crown was just below the upper slab.
Evaluation
At least three avalanche cycles in the last week have produced some very large full depth avalanches. The cycles cleaned out some of the paths leaving others hanging in balance, with weakest pockets pulling out here and there. Settlement has lessoned potential for initiating slides, but has also increased the possibility of resulting slide being quite large. Another round of wind has added yet another cap to the mix, with shallow recently formed wind drifts avalanching, possibly stepping down into crust facet interface.
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