Checking on buried surface hoar - Tumalo snow profile

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Updated:
Wednesday, Mar 20, 2019 7:47 PM
Observer(s):
Aaron Hartz
Position:
Pro Ob
Location:
Three Sisters Area (44.009715, -121.641762)
Ob Date/Time:
Wed, Mar 20, 2019 - 6:46 PM
Report Type:
Snow Conditions
Mode of Travel:
Ski or Snowboard

Written Report:
On the north side of Tumalo near treeline/below treeline, I found the buried surface hoar layer that we have been talking about for the last few weeks. I found a mix of well preserved surface hoar and some broken fragments. During snowpack tests, I got sudden results and propagation that are indicative of avalanches being possible on this weak layer.

There has not been any reported avalanche activity on this layer since last Friday. My hunch is that on many sunnier/warmer slopes, the surface hoar is breaking down and trending toward being inactive. However from what I saw today, on shaded/colder slopes, the buried SH can still be a failure point in the snowpack. It will be hard to trigger since there is 50 cm of firm snow on top of the weak layer, but if you ski over a shallow spot where the weak layer is closer to the surface, it will be possible to trigger a slab avalanche. The likelihood is decreasing, but the consequence is still high.

Ski quality was variable. I traveled over supportable crust, breakable crust, preserved powder, corn, and sticky mush throughout the day. I found pockets of shaded old powder on the north side.

Wind was light out of the SE most of the day.


Multimedia

Caption: Profile from Tumalo in the north trees