Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
Dallas Glass
Observation Date:
January 29, 2023
Submitted:
January 29, 2023
Zone or Region:
West South
Activity:
Snowmobiling/Snowbiking
Location:
White Pass: Hogback Mt Area

Triggered Avalanches

Did you trigger any avalanches? 
Yes
Was it intentional? 
Yes
Avalanche Type:
Soft Slab
Size:
Size 1: Relatively harmless to people
Elevation:
5800
Aspect:
E
Comments:
Small wind slab 8" deep and 20ft wide on a very steep convex rollover. The slide entrained loose surface snow and ran approx 50 vert feet.

Signs of Unstable Snow

Did you see shooting cracks? 
Yes, Isolated
Did you experience collapsing or whumpfing? 
No

Observations

Wind: Intense blowing snow, scoured slopes, eroded cornices, fresh cornices, textured surfaces, drifts, and firm hollow slabs. Signs of wind transported snow were abundant today. As I mentioned above, along ridges at upper elevations, the loading pattern was quite predictable. However, just a little lower in the terrain and winds seemed to come from every direction. It's worth noting that the one legitimate avalanche that I triggered was on an E aspect and winds were coming from the E. This just emphasizes the varied loading patterns on these mid-slope features.

New Snow: In wind-sheltered areas, there was about 5" of very light dry snow from yesterday afternoon and last night. On SE-SW aspects this new snow sits over a melt-freeze crust. It was very poorly bonded to this much firmer layer.

Snowpack: In general the MLK crust was down about 2ft (60cm). While I could still find other recent layers (1/21, 1/18) in the upper snowpack, none of them showed any lingering weak grains.

Media

This NE-E facing blowing is normally full of snow, but with this wind pattern, it is stripped down to old crust layers.
Intense blowing snow along Hogback Ridge with "fat" pillow-like drifts below.
Blowing snow and pillow-like drifts forming on W aspects.
Scoured slopes and drifted us discern local wind direction and possible loading patterns.
This small wind-loaded test slope failed and produced a very small slab 6-10in deep.
A snow profiles in the Miriam Creek Basin, N, 6100ft.
A long (15ft) shooting crack in a wind-loaded pocket N, 6500ft.

Advanced Observations

Observed Avalanche Problem #1: 
Wind Slab
Comments: 
At higher elevations, wind slabs were very firm and on more predictably loaded features.
At mid-elevations winds were forming slabs on various aspects and features. Loading patterns were much less predictable. Slabs on these mid-slope features were softer.
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