Observation: NWAC Forecaster

All Observations

Basic Information

Observation Date:

March 15, 2022

Submitted:

March 15, 2022

Observer:

NWAC Forecaster - Irene Henninger, Alyssa Young

Zone or Region:

West North

Location:

Heather Meadows (All aspects, 4200-5500ft)

Recent Avalanches?

Yes

Cracking?

None Experienced

Collapsing?

None Experienced

Bad visibility travel alert: My partner was skinning along in front of me and all of a sudden she disappeared. She fell 5+feet off a cornice into a gully. This is a relatively flat area we're familiar with and we no avalanche concerns in this location. My ski marks the edge of the cornice she fell off (not really visible, is it?) This nearly happened several other times.

During the storm, wind formed lips and drifted in around cornices.

Storm slab avalanche in Bagley Basin, probably failing within the new snow.

Advanced Information

Cloud Cover:

Overcast

Temperature:

30°F

Wind:

Calm

New/Recent Snowfall:

Storm starting 3/10 now has settled amounts of approx 2ft at 4200 and approx 3ft at 5000ft

Low clouds and flat light until 11 with moderate (S2) snowfall. Low clouds cleared, and snowfall lulled (still hi clouds) and we had some visibility til we left at 12. Snow surfaces were all fist-hard, and dry, with ski pen of 10-20cm, boot pen ~30cm.

Avalanche Observation Comments:

One natural D1.5 in Bagley Basin failing ~1-2ft deep during the storm. Aside from small loose dry avalanches in steep areas we didn't see any other natural avalanches, or trigger any, despite stomping on plenty of test slopes and small corniced slopes.

We stuck to low-angle terrain and small slopes. Slope tests on smaller, supported slopes were unreactive, leading to a false sense of security until digging, where we found a thick crust beneath the new snow layer (about 3 feet down at 5000ft, and dry) and test results failing above the crust. Triggered avalanches in nearby areas, failing about 3 feet deep confirmed our concerns with the pit results.

At 4200ft the storm snow layer was 2 feet deep, and all moist aside from 4" of low density, dry surface snow. There was a midway layer that was slightly harder than the snow above and below it. That layer and beneath it were moist-wet, and well bonded to the underlying layer.

Problem	Location	Distribution	Sensitivity	Size	Comments
Storm 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: 100cm/March10-15 Comments: Beneath the storm slab there is a crust with possible faceting above the crust. It is most likely in the upper NTL and ATL. Unknown how widespread this is.

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