Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
January 4, 2023
Submitted:
January 4, 2023
Observer:
NWAC Forecaster - Irene Henninger, Andrew Forsman
Zone or Region:
Stevens Pass
Location:
Big Chief Mountain (4000-5800ft)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

A thin crust formed at the surface from misting which occurred on 1/3 in the Stevens Pass zone. It was noticeable on all aspects and all elevations we traveled (4000-5800ft)
Another mist crust photo.
Moderate easterly winds caused small amounts of transport on ridgelines.
Riming occurring Jan 2-4 along ridgelines.
Wenatchee Bowl Pit. Consistent resistant planar moderate compression tests were failing halfway down the new snow layer above the Christmas crust. The slab on top was so soft it was not possible to remove it as a cohesive layer. This is likely the interface where previous human triggered avalanches occurred since our last snowfall Saturday.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
25°F
Wind:
Moderate , E

Active riming has been occurring for 3 days (1/2-1/4), noticeable along ridgelines in near and above treeline areas. Rime growths are about 3" thick, facing east, and most noticeable on trees and very steep snow-covered features along the ridgeline. Crusts coat many surfaces, meaning minimal snow is available for transport at the wind speeds we were seeing today.

Snowpack Observations

Noticeable in all treeless areas we traveled was a thin crust, formed on the surface from misting which occurred on 1/3. This misting event appeared to destroy much of the previously identified surface hoar.

We stopped to intermittently check snow along the top of Highlands Bowl (5000-5700ft, S, SE, E). The Christmas Crust was consistently buried 40-50cm deep. The steep south aspects had a thicker (~3cm) crust on the surface, formed from Sunday's sunny skies. This ranged in thickness depending on aspect and steepness changes.

Moderate sustained winds only transported small amounts of snow to just below the ridgeline (5000-5800ft), due to all the previously mentioned surface crusts. These shallow deposits were unreactive.

As soon as we dropped off the ridge onto the W/NW Wenatchee Bowl it was calm. We dug a pit at 5600ft, W. No older wind loading was present, and the Christmas Crust was 35cm deep. Our only test results were resistant planar moderate compression tests, failing about halfway down the new snow layer above the Christmas crust.


WordPress Lightbox