Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

I went to the South Fork of Bishop Creek to monitor the persistent slab problem in the southern end of the forecast area.

• I experienced many collapses and shooting cracks on northwest, north, and northeast-facing slopes between 9600 feet and my high point of 10100 feet.
• The snowpack was less than a meter deep. Below about 9500 feet rocks and brush stick up through the snow. Above that, on northerly slopes, the snow cover has been more continuous since before December 1st. I found big, weak, depth hoar grains at the bottom of the snowpack. This layer is the culprit that failed, causing all of my whumpfs and shooting cracks.
• I saw a few puffs of blowing snow from northerly winds in the morning, but that quickly subsided. Winds were calm where I traveled. I measured below-freezing air temps on shaded slopes, though the South Lake weather station marked a high of 47 deg. F at 1 pm.

I made an extra effort to plan a route that wouldn’t take me onto slopes steeper than about 30 degrees and would avoid complex, rocky terrain. All of those red flags made me glad I didn’t expose myself to triggering persistent slab avalanches.