Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 3, 2022
Submitted:
December 3, 2022
Observer:
NWAC Forecaster - Andy Harrington and Dallas Glass
Zone or Region:
Snoqualmie Pass
Location:
Alpental Ski Resort

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced

Media/Attachments

It was a beautiful but windy day on the ridgelines. Wind transport was easy to spot as were other visual clues to help guide our terrain choices.
A shooting crack in a wind-loaded pocket. One of the red-flag signs of instability that shouldn't be ignored.
Easterly winds easily transported low-density snow near ridgelines on 12/3. This wind-blown snow likely collected near the base of the cliffs and rocks seen in the foreground.
Actively blowing snow, freshly building sharp cornices, and textured surfaces. All easy to spot signs of wind-loading. Look for slabs to develop on the slopes on the left side of the picture.
Recent storm snow from this past week has settled some but still sits atop a series of crusts. Some weaker snow was found below the crusts, but we believe the snowpack to be generally strong as this point.
An intentionally triggered Wind Slab by a skier on a convex rollover. The snow in this area looked "fat", was stiffer, and on existed on a rocky convex slope.

Advanced Information

Weather Summary

New/Recent Snowfall:
~3"

It was a beautiful sunny but chilly and at times blustery day in the mountains. Down at pass level, the east flow cycled some low-level clouds in and out during the morning hours. We were out of the field by noon.

We were able to intentionally trigger a number of Wind Slabs on convex rollovers during our travels. One crown was easily over a foot at the thickest part. These unstable pockets were easy to spot as they had similar terrain characteristics and plenty of visual clues keyed us into where they were more prevalent.

Snowpack Observations

The snowpack has consolidated considerably and gained strength since we were last out on Thursday. Unfortunately, the winds have had their way with the snow in wind-prone areas, creating wind slabs on specific terrain features and firming up the low-density powder that many recreationalists enjoy. In wind-sheltered areas, low-density cold snow still exists but is not as deep as it was previously.

We dug to ground at 5200' on a N aspect near the top of Alp and found about 4.5 feet (136cm) of snow. We would categorize the snowpack as generally strong with roughly 2.5 feet of snow from this past week sitting above a series of crusts and mostly strong grains. We did find some previously weak snow just below the lower crust, but it appears to have been wetted and is gaining strength. Deep tap tests on this layer did not produce any noteworthy results.

Found some fantastic skiing at mid to lower elevations, but there are definitely still plenty of holes, boulders, creeks, and shrubs to watch out for.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
 Comments: Reactive to ski cuts on some slopes. More stubborn on others.
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