Observation: NWAC Observer

All Observations

Basic Information

Observation Details

Observation Date:
February 17, 2023
Submitted:
February 17, 2023
Observer:
NWAC Observer - Drew Lovell
Zone or Region:
East North
Location:
WA Pass Zone (most aspects 5000'-7500')

Signs of Unstable Snow

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

Media/Attachments

A super small Dry Loose sluff overran my ski tracks, when steep northwesterly terrain caught a blast of PM sun. A total non-issue, unless one was in the wrong place at the wrong time...
Moderate westerly PM winds were readily transporting recent low-density snow. I chose to avoid steep features that were undergoing active loading.
Many 10-day-old avalanche crowns may coincide with a layer of buried rounding facets, generally down 50-70cm around the zone.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
21°F
Wind:
Moderate , SW
New/Recent Snowfall:
About 5-8cm. This has added padding to the settled 15-20cm over the Feb.12 crust.

Another beautiful day. Partially obscured skies in the AM, with very brief, very light snow showers. Just a few clouds lingered in the environs, with darker, grayer places to the south and west. Winds generally built to moderate levels by the PM, channeled by local terrain. Recent low-density snow was loading isolated features, but also seemed to be sublimating.

Observed one micro Dry Loose that overran my tracks, when very steep, rocky northwesterly alpine terrain caught a blast of PM sunshine. See photo.

Snowpack Observations

Toured the headwaters of Early Winters, Copper Creek, and the North Fork Twisp River today.

Snow depths throughout hovered around 200-240cm, aside from loaded anomalies.

The recent 15-20cms overlying the Feb.12 temperature crust has gained some body, providing generally good ski quality. I found a good bond above the crust, and little concerning faceting (weakening) below. It is noteworthy that the crust changes in character from zone to zone. In general, it is thinner and weaker, at times almost indiscernible, in the colder valley bottoms (such as the North Fork Twisp River). In certain terrain along the crest, the crust is a legitimate, robust, 1cm thick MFcr.
Ski-testing some recently-loaded steep solar slopes today produced no results.

In a profile on a NE aspect at ~6400', the Feb.3 Interface presented as a 2-3cm thick layer of .5mm rounding faceted grains, down about 55cm. It yielded Hard Sudden Planar (x 2) results in Compression Tests. This interface seems to coincide with some of the 10-day-old but still visible avalanche crowns around the zone. The rounding Jan.5 SH was also visible in the pit wall of this profile, down about 100cm, amazingly still producing Hard SP results in Deep Tap Tests.

In another profile on a loaded S aspect at ~6800', the Feb.3 Interface was down 60cm, presented a similar grain type, and produced similar results. An ECT at this location suggested that propagation was unlikely. This interface may present as a melt-freeze crust in other solar locations.

Given the recent testing that the snowpack has received from warming (and rain!), aggressive snowmobiling, and fairly steep skiing, it seems unlikely that buried persistent grain types will re-emerge as avalanche problems. But the structure is nonetheless worthy of attention.

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