Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 31, 2022
Submitted:
December 31, 2022
Observer:
NWAC Forecaster - Katie Warren
Zone or Region:
East South
Location:
Ahtanum Meadows (3500-6900ft all aspects)

Signs of Unstable Snow

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

Media/Attachments

Small wind slabs that likely released between 12/29 and 12/30.
Crown from a wind slab is still visible, but slightly drifted in, just below the ridgeline.
Wind affected slopes. you can see the texturing and the drifts around trees indicating wind direction.
Small cornice formations with pillowlike wind slabs on the slope below.
A crown profile from one of two small wind slabs I observed. This crown was around 30cm deep and released in an older softer snow layer.
Fresh snow, Rimed trees, and some partly sunny skies made for a beautiful day out and good riding conditions.
Profile from a NNW slope at 6600ft. There was 190cm of snow in this location with 60cm over the Christmas Crust (located between the top two crystal cards)

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
25°F
Wind:
Moderate , W
New/Recent Snowfall:
Below 5000ft: HN 15-20cm, above 5500ft: HN 20-30cm

It was a pleasant day with mostly clear skies, although areas to the west were socked in with clouds and occasionally these would drift eastward into the Darland Mountain area for brief periods of time. Winds were mostly light and variable. Ridgelines had moderate gusts that would drift some snow around, but were not consistent enough to load slopes on lee aspects.

Wind Slab (24-48hrs old)
6800ft, East Aspect
HS-D1.5-R2-O

Snowpack Observations

Sheltered flat terrain at around 5000ft had approximately 75cm of snow, with 30cm of snow over the Christmas Crust. The new snow was well bonded to the crust and stability tests produced no results. The Christmas crust was around 15cm thick and supportable to boots and snowmobiles.

Total snow height increased as I gained elevation, with 100-120cm of snow at 6000ft and 190cm at 6600ft.

I dug a full profile at 6600ft on a NNW aspect and overall found a strong snowpack with 60cm of snow over the Christmas Crust. The crust in this location is around 20cm thick, knife hard, and very supportable. While the snow seemed well bonded to the crust and test slopes produced no results, I did get an ECTP 28 RP result on rounding stellars on top of the crust. Interestingly there is still dry snow below the crust, with a preserved layer of surface hoar directly beneath the crust. Out of curiosity, I did a PST on this layer with a result of 42/100 (END).

Truly, the most notable observations from today were some small (D1-1.5) hard wind slab avalanches that ran on easterly aspects near ridgelines at 6800ft. These had likely ran over 24hrs before I observed them. I was not able to get any wind-loaded test slopes to crack or produce any slabs today. Wind-affected snow was present in exposed terrain down to 5000ft.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 30cm 12/29-12/30