Observation: NWAC Observer

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Weather Summary

Overcast in the morning with light snow showers in the afternoon. Mostly calm to light winds. A couple gusts to moderate in the afternoon.

Avalanche Observations

#	Date	Location	Size	Type	Bed Sfc	Depth	Trigger	Photos	Details
1	Dec 27, 2022 ()	Head of hairpin Valley/ West aspect of Kangaroo W 6400ft	D2.5 R2	HS-Hard Slab	O-Old Snow	4ft	N-Natural		Report
1	Dec 24, 2022 ()	West aspect Kangaroo Ridge SW 7800ft	D3 R3	WS-Wet Slab			N-Natural		Report

In our travels of the hairpin valley we saw a variety of recent avalanches, which have released at different times in the last week on different interfaces. The first one we came across was the largest and oldest. On a West aspect of Kangaroo Ridge we found D3 debris which had about 30cm of new snow on it. The debris here had it's own crust, and we believe this released with the warm up and precipitation on Dec. 24th or 25th. We then traveled up the hairpin valley. As we traveled SE up the valley a deep crown was evident at the head of the valley. The debris of this avalanche appears to be 'fresher' and more recent than the previously mentioned avalanche. This newer debris had only 2" of new snow on it. We estimate it ran yesterday or more likely the day before on Tuesday the 27th. This appeared to be a D2.5 avalanche. We considered digging a crown profile, but decided to dig a pit nearby to avoid the exposure. More on that in the Snowpack Observations. Higher up we also saw small 3-6" wind slab which were very recent. Lastly, there were some one to two foot crowns now covered in the new snow. These were probably D1.5 releases from the Christmas warm up. A lot has been going on up there!

Snowpack Observations

Down in the Methow Valley surface hoar has been growing to 3-4mm. At 5100', at the hairpin, smaller surface hoar was about 1-2mm. As you gain in elevation wind effect becomes apparent and surface hoar goes away. The substantial Christmas crust is covered by about 14" of new snow. We dug a pit near the crown of the avalanche at the head of the hairpin valley, at 6400' on a NW aspect. The snow height here was 2 meters. Our culprit layer, the Dec. 8th buried surface hoar, was found 105cm down from the surface. The snow above and below the 12/8 interface is 1-2mm rounding facets. The Christmas crust stands out at about 12cm thick and quite hard. We did two column tests; an extended column test and a compression test. We got no results from the extended column test (ECTX). In our compression test there were some resistant planar fractures in the newer storm snow, but more significantly we had a sudden collapse result on the Dec. 8th interface. See video of Josh Cole performing this CT. (CTH SC at 105cm). It can be hard to know how to interpret mixed results from a couple column tests, but I think we can say that there is a weak layer down there, and if it were somehow triggered, it could produce a very large avalanche.

Avalanche Problems

Problem	Location	Distribution	Sensitivity	Size	Comments
Wind Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Layer Depth/Date: 20-40cm
Persistent Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Layer Depth/Date: 100 cm Weak Layer(s): Dec 8, 2022 (SH)