Observation: NWAC Forecaster

All Observations

Basic Information

Observation Date:

February 7, 2022

Submitted:

February 8, 2022

Observer:

NWAC Forecaster - Matt Primomo

Zone or Region:

East North

Location:

Varden Pk-Silverstar area (NW-E 3000-6,900ft)

Recent Avalanches?

None Observed

Cracking?

Widespread

Collapsing?

Isolated

Pronounced faceting on the underside of the upper melt freeze crust. From a north aspect at 5,500ft

Cracking on skin track. North at 5,600ft.

Recently created, stiff wind slab. NE at 6,400ft.

https://www.instagram.com/p/CZs_t96Ll74/

Advanced Information

Cloud Cover:

Mostly Sunny

Wind:

Moderate , SW

New/Recent Snowfall:

4-8" of recent snow

Very warm in the morning with a light rain shower or two moving through. Temperatures cooled off noticeably by the afternoon and at higher elevations.

Avalanche Observation Comments:

Observed a couple older WL slides in the D1.5 size off steep south-facing paths on Delancey.

Incredibly reactive with widespread cracking and localized collapsing from 3,200ft to 6,900ft on NW-E aspects. Above 6,600ft we experienced about 4 large whumphs. These were in areas where wind had created stiff wind slab (1F-P) resting over a faceted crust structure, and ranged in size from 5m to 15m around us. We were far enough away from large steep slopes that we couldn't tell if we had remotely triggered a slide or not. I don't believe we did, though.

3,200-5,000ft: Observed large surface hoar sitting directly over a ~1mm, clear freezing rain crust and recent HST was poorly to very poorly bonded. Surface snow was moist with the light rain showers, this may have contributed to the instability observed by causing the slab to become more cohesive. Instabilities were also observed with poor bonding of the freezing rain crust to the crust beneath it, and lower faceted layers sandwiched between crusts. ECTP's were failing upon isolation at one point.

5,000-6,000ft: Bonding of the HST over the crust was generally good to very good, though the crust became thinner with a more widespread crust/facet/crust structure (See profile image). Easy test results indicated propagation beneath the crumbly crust on very weak faceted grains.

6,000ft-6,900ft: Bonding of the HST over the crust was fair, with a thin (1cm) layer of 0.5mm facets often found (1/30). The crust itself became thinner (1-3cm). In exposed areas the crust was still exposed to the surface. The crust is brittle, with pronounced faceting on the underside of it. ECTP's in easy range failing on facets over the crust.

Problem	Location	Distribution	Sensitivity	Size	Comments
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: 12" Weak Layer(s): Jan 30, 2022 (FCsf) Comments: Perhaps not as problematic on steep S aspects.

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