Pacific Crest Trail @ Sonora

Location Name: 
Pacific Crest Trail @ Sonora
Region: 
BWRA
Date and time of observation: 
Sat, 04/22/2017 - 13:15
Location Map: 


Red Flags: 
Recent avalanche activity
Rapid warming

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

Many Wet-Loose avalanches have been seen all across the BWRA on all aspects above & below Treeline. It has been two evenings since we have had temperatures below freezing at our Snotel sites & rapid melting is taking place. Todays snowpit revealed something interesting just below a surface ice crust, slushy snow grains. In the snowscience realm it is called Radiation Recrystallization, but more commonly it is a thin layer of ice (or faceted snow) suspended on top of saturated slushy snow. The area where I dug my pit is a few hundred feet above the Snotels elevation & may have had a brief period of freezing & is on an exposed slope. The process occurs when (long wave) solar radiation is reflected by the snow surface & (short wave) radiation is absorbed just below the surface. This energy can sublimate snow (change form from solid to gas) and melt it, both can have unstable effects on the snowpack. If or when this slush freezes it will create a great gliding surface for possible faceted crystals & new snow to slide upon.

Aside of that issue melt-water has begun percolating through the snowpack & has collected above the 35cm depth in the pack. In my Shovel Shear test I could notice faceting along the Melt-Freeze Crust around 28cm down, possibly making this another weak layer interface to be mindful of.

Snowpit or crown profile photo or graph: 
Snowpack photos: 
Leavitt Cirque
PCT Pit
Leavitt Cirque
Above Sardine Falls
Weekend Parking
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
25% of the sky covered by clouds
Air temperature: 
Above Freezing
Wind Speed: 
Moderate
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: