Wind Slabs on Andesite

Andesite Peak provided a good venue to look for new wind slab formation on its upper slopes and to see how the new snow load was affecting the weak snow below the Jan 4th rain crust in sheltered areas.

As we skinned in the sheltered below treeline areas, we could feel the Jan 4 rain crust and the weak snow below it with almost every pole plant. We stopped and dug several quick hand pits to confirm what we felt with our poles. This layer did not show any signs of current instability since there was no slab on top of it. We still wanted to track its distribution and any changes in its strength before the forecasted storms next week. In a below treeline meadow, we stopped and dug a quick test pit. We found the snow stratigraphy matched what our pole probes and hand pits had revealed earlier. About 4-5 inches of new snow rested on top of the old snow surface. Below we found the Jan 4 rain crust with weak faceted snow underneath it. Our stability tests were consistent with our general observations and did not indicate signs of current instabilities on those facets (CTM @ 17 taps Brk, ECTN @ 20, PST 28/100 SF). We did artificially load the snowpack and perform an artificially loaded PST test that failed while we isolated it. This piece of evidence indicates that this layer may have problems supporting a large load of new snow such as what we might get next week. 

We continued up into more exposed near and above treeline terrain. We saw blowing snow and drifted snow on leeward aspects (N-NE-E). We chose our tour route carefully to use lower angle slopes that passed by several small wind-loaded test slopes. We kicked several of these test slopes and caused some shooting cracks 10 to 20 ft long. Newly formed cornices above the test slopes also failed easily with a few kicks. The deepest of the wind slabs measured about 10 to 12 inches thick on one of the test slopes. These signs of instability and the continued loading by new snow and wind lead us to chose lower angle terrain for our descent until we got back to lower elevation slopes without wind exposure.