Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 20, 2022
Submitted:
December 20, 2022
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
Snoqualmie Pass
Location:
Kendall Trees

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Widespread
Collapsing? 
None Experienced

Media/Attachments

Slab triggered while traveling up Commonwealth Basin
Shooting crack and blocks failing during an uptrack test
15cm (6 inches) of snow fell on the car during my 3 hour observation tour
Snowpit at the top of Kendall Trees
One of countless D1 slabs found in Commonwealth Basin on 12/20.

Advanced Information

Weather Summary

New/Recent Snowfall:
About 6" of new snow when we started the day and 6 more fell in the 3 hours we were away from the car

It went from steady snow to borderline nuking out there at times with 2"/hour rates. We were somehow away from the winds, but others told us that the winds were cranking in an area they had visited.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
30 Dec 20, 2022
() 		Commonwealth Basin
W ft 		D1 I-New/Old Interface 0.5ft N-Natural
One of countless D1 slabs found in Commonwealth Basin on 12/20.
Slab triggered while traveling up Commonwealth Basin
Public Field Report: Cave Ridge
Public Field Report: Cave Ridge
Public Field Report: Cave Ridge
Remotely triggered from above. Notice shooting cracks above from my ski track.
Public Field Report: Summit Central
Shooting cracks radiating from the skin track on adjacent slopes. Approx 20’. WSW, 3300’.
This was triggered remotely while breaking trail and is indicative of the reactivity found throughout the zone.
A remotely triggered small storm slab in a gully adjacent the skin track. Shooting crack (~30’) and slide are outlined in red. WSW, 3400’.
Report
Commonwealth Basin

Widespread D1 slabs were observed in the BTL and NTL (small in many). Did not observe anything large enough to be called a D2, but some skiers mentioned they had found a larger one.

Snowpack Observations

The conditions in the Kendall area are well documented by our public contributors on the observation page. The snowpack was extremely sensitive in the morning hours, with remotely triggered slabs and a crown on almost every convexity or unsupported slope you could spot. We traveled to the top of the trees and just poked our heads out near the top. We observed some snow transport but were surprised at the lack of wind. Digging a quick pit, I got easy results at the new/old interface and at the 12/18 layer. Judging by the depth of most crowns I measured (5-7 inches), the thought is that most of these slabs were failing on low-density snow from the start of the storm (before the bump in temperatures). At the 12/18 interface, I was able to still identify some weak snow and rimed precipitation particles.

Blocks were failing easily on uptrack tests and it was easy to know that it was a heads up day right off the bat with so many signs of instability right in your face.

10:40 am
4780' SW
HS 132cm
HN ~15cm
12/18 @ 26cm
CT2 on new/old
CT7 on 12/18
ECTN9 on 12/18

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Storm Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 13-18 cm
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