Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
February 12, 2023
Submitted:
February 12, 2023
Observer:
NWAC Forecaster - Josh Hirshberg, Irene Henninger
Zone or Region:
Stevens Pass
Location:
Lake Josephine (N-E-SE, W, 3,500-5,360ft)

Signs of Unstable Snow

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

Media/Attachments

A faint crown of a natural avalanche that occurred on 2/8 in the Christmas Bowl area near Lake Josephine. N, 5250ft
A small natural avalanche that likely ran on 2/8 on the MLK crust. This images was taken on the 10th and is in the track of the avalanche that would be triggered by skiers on overhead slopes on the 11th.
Loose wet avalanches began Feb 10th in the apron of the Fluer de Lis area. Mill creek, N 4,400-3,800ft
A crown profile from a skier-triggered avalanche. The slide was 78cm deep, running on a thin weak layer on MLK crust. Near Lake Josephine, 5380ft, NE
Crown profile for a skier triggered avalanche that partially buried 1 skier on point 5463ft, just north of Josephine Lake. NE, 5380ft
The weak layer was predominantly rounded grains with slight facetting. It's difficult to identify any faceted forms. This rested the stout MLK crust. 1mm grid.
A cavity of weak snow surrounding a rock at the crown of a human triggered avalanche. HS-ASu-R2-D2-O. NE, 5,380ft, Pt. 5463 near lake Susan Jane.
Most of the crown of a human triggered avalanche in the Stevens Pass backcountry with suspected locations shown. HS-ASu-R2-D2-O
Crown profile location where slab depth was ~80cm. Human triggered avalanche in the Stevens Pass backcountry. HS-ASu-R2-D2-O
A human triggered avalanche in the Stevens Pass backcountry. ENE, 5400' HS-ASu-R2-D2-O
A human triggered avalanche in the Stevens Pass backcountry. ENE, 5400' HS-ASu-R2-D2-O
A human triggered avalanche in the Stevens Pass backcountry. An old crown from a natural avalanche (2/8) can be seen in the foreground, just right of the closest tree and is featured in another image. ENE, 5400' HS-ASu-R2-D2-O
https://nwac.us/public-obs/19565/

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Wind:
Calm

The day started warm with temperature inversions and scattered clouds. Temperatures were above freezing at 7a at 5,000ft. Skies became overcast by 11a with high clouds allowing some "green-housing" into the afternoon.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Feb 12, 2023 12:00 pm
() 		Jove Peak
S 5700ft 		D3 O-Old Snow N-Natural
Public Field Report: Jove Peak
Report
1 Feb 11, 2023 11:00 am
() 		Josephine Lake- Shoulda, Coulda
NE 5380ft 		D2
R2 		HS-Hard Slab O-Old Snow 2.5ft AS-Skier
u-Unintentional
View of the upper crown and start zone.
Looking down the track at the debris and burial location.
Showing the toe of the debris, aprx 4,800ft
A cavity of weak snow surrounding a rock at the crown of a human triggered avalanche. HS-ASu-R2-D2-O. NE, 5,380ft, Pt. 5463 near lake Susan Jane.
Crown profile location where slab depth was ~80cm. Human triggered avalanche in the Stevens Pass backcountry. HS-ASu-R2-D2-O
The weak layer was predominantly rounded grains with slight facetting. It's difficult to identify any faceted forms. This rested the stout MLK crust. 1mm grid.
A crown profile from a skier-triggered avalanche. The slide was 78cm deep, running on a thin weak layer on MLK crust. Near Lake Josephine, 5380ft, NE
Crown profile for a skier triggered avalanche that partially buried 1 skier on point 5463ft, just north of Josephine Lake. NE, 5380ft
Most of the crown of a human triggered avalanche in the Stevens Pass backcountry with suspected locations shown. HS-ASu-R2-D2-O
A close up view of the top of the crown of a human triggered avalanche in the Stevens Pass backcountry. Trigger point was below the photo. HS-ASu-R2-D2-O
Report
4 Feb 8, 2023
() 		Lumiere Ridge, Rooster Comb
NE 5400ft 		D2
R2 		HS-Hard Slab 2.5ft N-Natural
The crown of a large natural avalanche that likely ran in the early morning of Feb 8th on a wind-loaded slope outside of Stevens Pass Resort. Upper Mill Creek, NE, 5,400ft
Debris from natural avalanches occurring on 2/8 above Lake Susan Jane. North aspect
Crowns of 3 natural avalanches that occurred on 2/8 above Lake Susan Jane. NE, 5,400-5,200ft.
Report
Jove Peak
Josephine Lake- Shoulda, Coulda
Lumiere Ridge, Rooster Comb

Snowpack Observations

Our primary objective was to investigate a skier-triggered avalanche, resulting in partial burial on 2/11, in an area known as Shoulda, Coulda, Woulda, near Lake Josephine. The party involved with the avalanche originally posted an observation here.

We gained better views of other avalanches and debris in the area from the 2/8 cycle.

In open terrain, surfaces became moist on all aspects up to at least 5,000ft. Solar aspects have formed significant crusts over the past few days. Below 5,000ft and near trees, the surfaces were moist at 9a and became wet as the day went on. Moist to wet tree bombs gave way to canopy melting and "raining" in the afternoon.
On a steep, S slope, 5350ft at 11:30a- The surface was moist and breaking down. The top 11cm had transformed to melt forms and were frozen below the surface. Below that was dry snow.

A crown profile found that the skier-triggered avalanche, near Lake Josephine ran immediately above the MLK crust. At this location, the weak layer was 2cm thick layer of +4 finger hardness and 0.5mm mostly rounded grains (with slight facetting) resting the crust. See attached profile and avalanche observations for more details.

As we descended, we saw extensive moist to wet surfaces, rollerballs, and some loose wet avalanches.

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