Small isolated hard wind slabs on Donner Peak

Location Name: 
Donner Peak
Region: 
Donner Summit Area
Date and time of observation: 
Tue, 02/26/2013 - 12:30
Location Map: 
United States
39° 18' 41.364" N, 120° 19' 13.8216" W
See map: Google Maps
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

Most exposed areas on all aspects of Donner Peak exhibited signs of wind scouring. In some areas the winds had scoured slopes back to old crusts, and in others they left firm wind packed surfaces behind. Hard wind slabs still exited on all aspects in this area as well. These slabs were sporadic and isolated in distribution. They existed in some paces and not in other similar locations. All of the wind slabs observed today were relatively small in terms of their width and length. The largest of the slabs was about 25X30 ft. In depth they ranged from 4-6 inches to 2-3 ft. at the deepest spots. These slabs rested on top of layers of weaker snow where ever they existed. Tests on the slabs today resulted in more consistent unstable results and data seems to indicate that the weak layers below the slabs may be getting weaker. Even though formal tests did indicate that fractures can travel along the weaknesses below the slabs, single person ski cuts, ski kicks, and aggressively jumping up and down on test slopes produced no cracks, collapses, or other signs of weakness on intact slopes. Aggressive weighting of slopes that had been previously undercut did produce some small cracks. In this area yesterday, a group of several people standing on one of these hard slabs did produce a long shooting crack and collapse the weak layer.

Snowpit: From a NW facing test slope with a the thickest wind slab observed today in near treeline terrain.

Photo 1: Wind scoured surfaces were the most common snow surface observed on Donner Peak today.

Photo 2: A NE facing test slope at about 6900 ft. This crack occurred after I undercut the slope then aggressively weighted it by jumping on the slab in my boots. It did not respond to ski cuts or jumping on it with my skis even after I undercut the test slope.

Video 1: ECTP on the upper elevation NW facing test slope

Video 2: Trying to break the slab above my pit on the upper  elevation NW facing test slope

Video 3: ECTP on the lower elevation NE facing test slope pictured in photo 2.

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

MVI 2537

MVI 2538

MVI 2539

Weather Observations
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Below Freezing
Wind Speed: 
Moderate
Precipitation: 
Air temperature trend: 
Static
Wind Direction: 
Northeast
Accumulation rate: 
More detailed information about the weather: