Shallow wind loading and snow on Andesite Ridge

Location Name: 
Andesite Ridge
Region: 
Donner Summit Area
Date and time of observation: 
Mon, 02/14/2011 - 12:30
Location Map: 
United States
39° 21' 3.5712" N, 120° 21' 56.6604" W
See map: Google Maps
US


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

About 1 inch of new snow had accumulated in this area by 1pm. Snow continued to fall and seemed to increase in intensity around that time. In most areas the new snow fell on firm, frozen crusts resulting in "dust on crust" conditions. On the mid-elevation sheltered northerly aspects the new snow fell on top the softer, weaker snow snow left over from the last storm on Jan 30th. Handpits and ski cuts indicated that the new snow seems to be bonding to the old snow surfaces nicely. Some, small, isolated wind-loaded pockets up to 4 inches deep had formed on a few N-NE facing slopes near treeline. These pockets did not cover more than a few feet of any slope before they dissappeared. Where they existed, some skier triggered cracking and failures did occur due to a weakness in the new snow.

Photo 1 and Video 1: One of the small pockets of wind slab. Ski cuts on the rest of this slope did not result in any failures. Same slope as video 1.

Photo 2: Small skier triggered cracking in a small wind slab. This area of instability was only as large as what is in the photo. Ski cuts on the areas adjacent to the photo did not result in any fractures.

Video 2: Ski cut on a wind-loaded, NE-facing slope resulting in no failure.

Snowpack photos: 
Snowpit videos (tests, etc): 

20110214Andesite 001

20110214Andesite 006

Weather Observations
Blowing Snow: 
Yes
Cloud Cover: 
100% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Precipitation: 
Snow
Air temperature trend: 
Cooling
Wind Direction: 
Southwest
Accumulation rate: 
Less than 1 in. per hour
More detailed information about the weather: 

Strong winds all day. Snow showers were more intense than forecasted at this location and resulting in 1-1.5 inches of accumlation.