Wind slabs on Silver Peak.

Location Name: 
Silver Peak
Region: 
Cabin Creek, Deep Creek, or Pole Creek Area
Observation Date & Time: 
Thursday, February 23, 2023 - 11:45
Location: 
39.223310, -120.243696
Is this an Avalanche Observation?: 
Yes


Conditions Alerts:


Terrain Alerts: 
Slopes Steeper than 30 degrees
Obvious Slide Path
Terrain Matches the Advisory

Observation made by: Forecaster

Tabs

Observation
Description of Snow, Weather, and Avalanche Conditions: 

We toured on Silver Peak today to look at storm slabs and wind slabs. Snowfall rates were generally at 1 inch per hour, sometimes a little more. Once we reached 7,400' at 11:45 am, storm snow depths were notably deeper with around 1.5 feet of new snow on top of the Feb 21 old snow surface.

Breaking trail on our approach and on Silver Peak, we saw limited and only very minor storm slab cracking in wind protected areas. In the few places where we triggered some small cracks, the failure was occurring on graupel within the storm snow. We ski cut a few below treeline test slopes with no failures.

As we approached the ridgetop, the presence of wind slabs was obvious as the snow we were breaking trail through stiffened considerably. In some areas, wind slabs around 1 foot thick were 4F hard at the surface and 1F hard at the bottom of the slab. These wind slabs sat on top of 4F hard storm snow. We had to get right up to the edge of any wind slabs to make them fail. In the few places where we were able to do so safely, this triggered shooting cracks and small wind slab avalanches. The cracks were failing 1 foot+ deep into the storm snow with shallower avalanche activity occurring.

Hide Avalanche Details
Avalanche Type: 
Wind Slab
Failure Plane/Weak Layer: 
Storm Snow
Hide Trigger
Trigger: 
Skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
32degrees
Aspect: 
North
Starting Elevation: 
near-treeline
Hide Size
Destructive Size: 
D1 Relatively harmless to people.
Crown Height: 
Less than 1 ft
Hide Weather Details
Elevation of Observation: 
6000-7000 ft.
7000 - 8000 ft.
Blowing Snow: 
Intense
Wind Direction: 
Southwest
Wind Speed: 
Strong
Sky Cover: 
Overcast - Cloudy - 8/8 covered
Highest Precipitation Rate: 
Moderate Snowfall (S2 = 2 cm /~1 in per hour)
Precipitation: 
Snow
Air temperature: 
Below Freezing
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