Persistent Slabs Above Treeline North Aspects

Location Name: 
Persistent Slabs Above Treeline North Aspects
Region: 
Williams Lake Area
Date and time of observation: 
Thu, 01/11/2018 - 13:52
Location Map: 
United States
36° 32' 59.5896" N, 105° 25' 45.3648" W
US


Red Flags: 
Whumphing noises, shooting cracks, or collapsing
Recent loading by new snow, wind, or rain
Obvious avalanche path

Observation made by: Forecaster
Snowpit Observations
More detailed information about the snowpack: 

2 to 4 inches of new snow fell overnight with little wind.  It was nice to see the mountains white but it wasn't enough snow to make lower elevation travel managable on skis.  Even with cold temperatures it's amazing how quickly the snow melts on south aspects with our strong sun.  Winds were calm and we didn't notice any snow moving.  The snow that fell overnight was low density light powder and we didn't observe any wind slabs at all elevations.  We've been montitoring our poor snowpack structure above treeline on north aspects throughout the season.  On Tuesday we were able to get one whoomphing collapse.  Today we were able to initiate failure and release of several steep north facing slopes above treeline.  None of the slabs were able to overcome friction, but it speaks volumes that .1 to .2 inches of low density snow with no wind loading is enough to potentially tip the scales with our weak snowpack.  These slopes are not well connected with a continous slab, that limits our propagation potential, but the cross-loaded slopes that have snow from November are surprisingly deep (up to 4 feet) for the little snow we've gotten so far this year. 

Photo 1:  The poor snowpack structure that we have on north aspects above treeline. 

Photo 2:  Cross-loaded gully on a north aspect above treeline that wasn't able to overcome friction releasing down the slope

Photo 3: The low density light powder that fell Wednesday night.  Even though it's not much, it was making me wish I had my skis

Snowpack photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Calm
Precipitation: 
Air temperature trend: 
Wind Direction: 
Northwest
Accumulation rate: 
More detailed information about the weather: