Observation: NWAC Forecaster

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Basic Information

Observation Details

Observation Date:
March 9, 2022
Submitted:
March 9, 2022
Observer:
NWAC Forecaster - Andy Harrington
Zone or Region:
Snoqualmie Pass
Location:
North Slope of Chair Peak

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

The largest Dry Loose avalanche I was able to trigger. The low-density snow ran easily on the firm icy surface below.
On some northerly slopes at upper elevations, low-density new snow is now overlaying weak snow on top of a firm and icy crust created by last week's atmospheric river. In some areas, a hard Wind Slab also exists.
Weak snow was found just below a hard Wind Slab (~6" down) on the North Slope of Chair Peak on 3/9/22. (N 4800')
Signs of the wind's influence were easy to spot on the North Slope of Chair Peak on 3/9. Textured surfaces and large smooth pillow-like drifts. Not surprisingly, Wind Slabs were also found.
Very small skier triggered Dry Loose avalanche.
Here you can see a few blocks of Wind Slab I was able to trigger on a convex slope. Can't really call this one an avalanche, but more of a test slope.
The new snow has helped, but wasn't enough to bury the effects of last week's atmospheric river event.

Advanced Information

Weather Summary

New/Recent Snowfall:
Generally around 11cm HST

Mostly cloudy with periods of sunshine. A few flurries here and there didn't add much to storm accumulations. Calm winds.

Was easily triggering Dry Loose "avalanches". Many of them did not grow large enough to be considered much of an avalanche, but in the right terrain, they certainly could. One slide approached D1.
There was plenty of wind-stiffened snow to go along with isolated areas of hardened Wind Slabs. I jumped on multiple convexities and mostly triggered the loose avalanches. In a few areas I was able to get some small blocks of Wind Slab to fail, but nothing you would call an avalanche.

Snowpack Observations

I found about 7-8cm at lower elevations over the atmospheric river crust. Not enough snow to drive much hazard and not enough to cover up the most recent avalanche debris. That said, it did help with travel conditions some. Skin track was still quick slick BTL, though.

As I ascended in elevation, new snow depths increased and generally speaking I found about 11cm of new snow over the crust. This varied a little based on wind deposition and elevation. I found the crust to be boot supportable at all elevations where I checked.

On northerly facing slopes at upper elevations, conditions changed. There were obvious signs of wind-effect, with large drifts and textured surfaces. Some fresh and tender mini-cornices had formed near ridgelines. I jumped on multiple convexities and ski cut some others, but didn't have much luck triggering an avalanche. Still, whenever I dug quick pits, hard Wind Slabs were easily identified. Below the slabs, last week's storm snow (~8cm) sat above the atmospheric river crust, increasing the amount of snow over the crust into the 20-30cm range. This previous snow was obviously weak in many areas and is an area of concern for the time being.

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