The cloud ceiling was at about 8000ft. Cold! Occasional moderate wind gusts were still transporting small amounts of snow, but the major event was yesterday and textured, firm snow surfaces were aplenty.
A crown profile was conducted on the very large avalanche that occurred yesterday on the Shuksan Arm:
The snow depth where we dug was 370cm, and the thin (Solstice) surface hoar layer which the avalanche failed on was 70cm below the surface. From the surface, the top 10cm were 1Finger hard (wind-affected), and the 10cm below that were Fist hard, and there were barely discernable .5mm faceting (weak) forms in that layer. Beneath that was decomposing forms and rounds slowly increasing in hardness from 1 finger to pencil hard all the way to above the surface hoar layer.
3mm surface hoar crystals (persistent weak layer which the avalanche failed on) were still well developed and easily identifiable, both in the pit wall and on a crystal card. Other areas along the crown wall had crown heights up to about 150cm. Avalanche width was around 500ft, and we estimate it ran 800-1000ft, but were unable to see the final debris pile as it was hidden behind a roll.
On the return trip, we found wind-affected snow until about 4500 feet: Some areas were very slabby and made for challenging skiing, while a shift over a subtle feature would then deliver us onto low-density powder.
|Deep Persistent Slab
Layer Depth/Date: 70
Comments: SH/weak layer starts at about 4800ft in elevation and up, and unclear as to its' distribution- many areas were destroyed before they were buried 12/21 (Solstice)