Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 14, 2021
Submitted:
December 14, 2021
Observer:
NWAC Forecaster - Josh Hirshberg
Zone or Region:
East North
Location:
WA Pass (N-NW, 5400-7360ft)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

Subtly faceted grains above the "late November crust." Washington Pass
Profile with 160cm height of snow. The card marks the late November crust, where tests produced sudden and propagating results (CTM12 SC, ECTP20). NW, 7300ft, Washington Pass
The card marks the late November crust, where this compression test produced sudden results (CTM12 SC). NW, 7300ft, Washington Pass
The Hairpin Valley on Highway 20, Washington Pass
Whistler and Cutthroat Peaks. Washington Pass

Advanced Information

Weather Summary

Wind:
Calm
New/Recent Snowfall:
HN 15cm at WA Pass, 25cm in Winthrop

Cloud cover started as clear to FEW at dawn, becoming overcast (thin) by 10:00, then breaking at 14:00 and finally clear by sunset. Winds were calm to light. Very cold temperatures all day.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Dec 11, 2021
() 		WA Pass Hwy 20
NW 7600ft 		D2 SS-Soft Slab 3.5ft N-Natural
Natural avalanche, D2, likely occurred on Dec 11. Washington Pass, Liberty Bowl, 7,600ft, NW
Natural avalanche, D2, likely occurred on Dec 11. Washington Pass, Liberty Bowl, 7,600ft, NW
Report
3 Dec 11, 2021
() 		WA Pass Hwy 20- Liberty Bell paths
NE 7000ft 		D2.5 N-Natural Report
WA Pass Hwy 20
WA Pass Hwy 20- Liberty Bell paths

Many of the Liberty Bell paths ran (likely Saturday) w debris piles on Hwy 20 size D1-2.5

Snowpack Observations

Surfaces were very low density, cold snow at all elevations. Height of snow near and above treeline was 150-220cm.
Profile at 7300ft, NW
HS 160cm w favorable "right-side-up" hardness profile
Sudden and propagating results (CTM12 SC, ECTP 20) on 0.5-1.0 (minimally) faceted rounded grains above "late Nov" rain crust (buried 12/4) .
Profile At 6580ft, NW
HS 180
Sudden results (CTM11 SC) on late Nov crust at 90cm.
While we experienced no other signs of instability, the test results caused us to make conservative terrain choices.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
 Unknown
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 12/11-12

We were not able to assess wind slabs directly. The alpine terrain where we traveled was blanketed w uncohesive snow. Alpine faces on Kangaroo Ridge and The Needles in Pine Creek are still showing evidence of W wind transport from the weekend. Heard 2nd hand reports of wind-affected snow surfaces in Whistler Bowl nearest to Cutthroat pk.

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