3-21-06, Gog

(Unintentionally triggered slab avalanche)

There are still some steep slopes where you might trigger a slab avalanche stepping into older snow.  This afternoon we found one of these slabs lurking on the steep east face of Gog in Upper White Pine Canyon.

 As the third and final skier to descend the upper elevation 40+ degree east facing slope, I didn't really expect to trigger an avalanche, but I did.

I caught a peripheral view of the slope fracturing beside me and was able to escape to the side and off the moving slab.  I yelled warnings to my partners, who despite being safely out of the direct line of the descending avalanche, crouched for cover and gripped tree branches as the slide ran down the steep chute beside them.

  The unintentionally triggered avalanche was 40to 50 feet wide and 18 to 20 inches deep at the crown, running approximately 500 vertical feet.  It failed on sugary or faceted snow just under a thin sun-crust, which formed a week ago on March 14th and was then buried by the subsequent productive week's-worth of snow, (containing well over 3 inches of water).  See nearby pit

In Upper White Pine Canyon, a couple slabs naturally avalanched with heavy snowfall this weekend.  These are steep east facing slopes at 9000'.  Recent avalanche activity on similar slopes to the ones you want to ride should ring alarm bells.  The first skier to descend the slope that I later triggered reported shooting cracks in the area of the avalanche.  At this point we had committed to the line, but shooting cracks are another sure sign of instability.

On slopes with no underlying sun-crust and associated sugary weak layer, slab avalanches weren't the issue.  Loads of snow, shed from trees on 3-21-06 caused numerous dry point-release avalanches or sluffs on steep slopes.  This one ran around 900' vert.  Compared to slab avalanches, loose dry sluffs are usually much less dangerous.