Testing and Tracking The Deep Facets, Lake Mary Ridge

SNOWPACK OBSERVATION
Submission Info
Forecaster
Monday, March 5, 2018 - 1:00pm
Red Flags: 
37° 35' 12.642" N, 119° 0' 3.0636" W
Snowpit Observations
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Toured up the Lake Mary Ridge to ~9900' below TJ Bowl tracking and testing the deep facet layers. The facets are deeply buried -- between 95 and 150cm down -- but reactive in deep tap and propagation saw tests.

We started the day by digging several profiles across a N and NE facing slope at about 9000' (see sample profile). The facets in this area were 120cm down. The layer of concern, across all of the 3 profiles was F hard 2mm facets under a 1F hard breakable melt-freeze crust or directly under 1F-4F wind deposited rounds (see crystal card photo). Deep tap test results across the slope were generally DTM SC in this layer. Propagation saw test results in one of the deep facet layers showed potential for fracture propagation (see profile). Temperature gradients around the facets indicates that the layer may be slowly weakening (change T/10cm greater or equal to 1 deg C) After digging we tracked the facets with a probe up and across the slope and found it consistently up to about 9800' where it started to be more hit and miss (see map). Another round of deep tap tests at 9900' to confirm the layer had simialr results to down below: DT14 SP down 150cm x2. Suprisingly, this is the first time I've seen this layer on W and E facing aspects rather than just northerly slopes. However, they seem to have a wider distribution on NW-N-NE slopes. On true W and E slopes and above 9800' the layers seemed to become more specific to isolated. We ran out of time and didn't track the layer above 10,000'.

My general impression is that if this layer can be triggered, by a big cornice fall, a snowmobile landing a jump, or a smaller avalanche for example, you'll have big trouble. We did not have any whumphing or collapsing today, I expect because of how deep the layer is in that area.

By afternoon all aspects except true N were beginning to change to melt-freeze at the surface (especially where there is tree cover to reflect the radiation back down).

Snowpit or crown profile photo or graph: 
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Weather Observations
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