Wind Slab Obs

April 29, 2022 at 12:00 PM
Name: Kate Moynihan| MWAC
Location: Right of Lunch Rocks

I traveled into the bowl today to assess the wind slabs that developed Wednesday through Thursday. I was specifically looking for the softer slabs in protected areas to see how reactive they were. Here is what I found:

Traveling to approximately 4600’ on lookers-right of Lunch Rocks there were various densities in the wind slab from 30” boot penetration (4F hardness) to 2” boot penetration (P hardness). The differences were specifically where the snow was more protected. These protected areas were the deep soft slabs. Any place that had full exposure to the NW wind was stiff and unreactive in hand shear tests.

In a protected area, I dug a pit down to the old bed surface, 55cm deep, and found several layers within the new slab 4F-1F hardness with the top 5-12cm at P hardness. This top layer was the most reactive in tests (CT11 SC & CT13 SC). However, there was no propagation of this layer (ECTN11 & ECTN12). The reactive layer was likely from the higher winds Thursday afternoon while temps were well below freezing.

There was some sun earlier in the day that started to affect the top cm of snow, but temps were still below freezing and clouds came in which stopped any solar radiation in the snowpack. Some wind loading was still happening when I was leaving but there was limited snow to transport.