Potential developing persistent slabs on Rubicon Peak.

Location Name: 
Rubicon Peak
Region: 
West Shore Area
Date and time of observation: 
Thu, 03/27/2014 - 11:30
Location Map: 
United States
38° 59' 23.3808" N, 120° 8' 2.7672" W
See map: Google Maps
US


Red Flags: 
Recent loading by new snow, wind, or rain
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

Wind slabs and storm slabs were present in this area, but the most significant findings were indications of a developing persistent slab problem near treeline and below treeline on NW-N-NE aspects. Near crust facets just below the old snow/storm snow interface showed the ability to propagate in formal snowpit tests (PST), but the overlying snow load has yet to reach a critical level. Upcoming significant snowfall events Friday night into Saturday and another potential storm event Monday could add sufficient snow load to overcome the strength of the near crust facet weak layer.

Wind slabs in near treeline terrain showed no results in formal snowpit tests. Informal observations did not reveal any additional signs of instability such as cracking or test slope failures in this specific area. A skier triggered wind slab avalanche was reported from near Grouse Rocks (Ward Canyon area) this morning.

The first ascent party on Rubicon this morning reported minor cracking while trail breaking in wind protected areas. At 10 am, frequent departures from the existing skin track revealed no additional cracking while breaking trail. Small shooting cracks were created only in previously undercut areas while passing within one meter upslope of the undercut track.

Rapid warming of the snow surface below 7,500' was observed on all aspects at 1:45 pm during breaks in cloud cover.

Video: Showing the potentially problematic near crust facet layer.

Snowpit or crown profile photo or graph: 
Snowpit videos (tests, etc): 

20140327 Near crust facets on Rubicon Peak

Weather Observations
Blowing Snow: 
Yes
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Cloud cover was at 100% through mid day. Around 1 pm breaks in the cloud cover began to occur with cloud cover decreasing to 50% sky coverage at times.