Widespread natural avalanches below treeline on Jake's Peak.

Location Name: 
Jake's Peak
Region: 
West Shore Area
Date and time of avalanche (best estimate if unknown): 
Thu, 02/18/2016 - 06:00
Location Map: 
United States
38° 58' 10.3332" N, 120° 6' 53.172" W
See map: Google Maps
US


Red Flags: 
Recent avalanche activity
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path
Observation made by: Public
Avalanche Observations
Avalanche Type: 
Dry
Slab
Slope: 
42degrees
Trigger type: 
Natural
Crown Height: 
1 ft
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Avalanche Width: 
100ft.
Terrain: 
Below Treeline
Elevation: 
8 400ft.
Bed Surface: 
Storm Snow
Avalanche Length: 
200ft.
Number of similar avalanches: 
5-10
More detailed information about the avalanche: 

Numerous natural avalanches occurred in the early hours this morning on Jake's Peak. All avalanches were observed in below treeline terrain on NE aspects above 8,000'. All avalanches failed within the storm snow and a density change of F+ hard storm snow on top of F hard snow snow. This layering was easily identified in hand pits at the bottom of the peak and was noted in all inspected areas while ascending. This weak layer was around 15 cm above the old/new snow interface. HN in this area was easily 40 to 60 cm. Above 8,000' where the overlying slabs become slightly stiffer from wind effect, avalanche activity had occurred. Crown lines and debris were covered under 3 to 6 inches of new snow. Most of the avalanches appeared to have failed naturally. A couple may have been skier/snowboarder triggered where debris overran the skin track and were covered by lower end new snow amounts. All avalanche crowns 30 to 45 cm deep were on steep micro terrain features where slope angle was 40 to 44 degrees. Skier triggered cracking was still occurring around noon while breaking trail and while cutting micro terrain slope convexities.

Photos 1,3,4,5 - Partially refilled crown lines.

Photo 2 - Debris under 6 inches of new snow from one of the larger avalanches noted.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
75% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Snow
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour