Snow surface cracking near treeline on Trimmer Peak.

We toured Trimmer Peak today, getting a good picture of conditions across the 6,500' to 9,500' elevation range on northerly aspects. As we ascended the Jan 4 rain crust was prominent below 6 inches or less of storm snow up to about 6,750'. It disappeared fairly abruptly as we continued to ascend. As we neared 8,500', still in below treeline terrain, we began to experience very localized but consistent cracking and collapse of the skin track. Only very small areas less than one foot in diameter immediately under foot would crack and collapse. I dug a hand pit out the bottom of the skin track and identified lower density, F hard snow below the New Year's upside-down layer as where the failure was occurring. We dug a test pit here and had all ECTN results.

We continued to ascend and as we transitioned into near treeline terrain at about 8,800' with a little exposure to previous SW winds we began to trigger snow surface cracks running up to four feet perpendicular to our skis. Again we stopped and dug a test pit. Again we had only ECTN results. Digging out a crack by hand revealed that the crack went about 1.5 feet down through recent storm snow to the same New Year's upside-down layer. There was no crust here or signs of faceting, only a density change. It appeared that the slight wind stiffening of the snow surface that existed near treeline enhanced the slab properties enough to allow for the cracking.

Once on the ridgetop and in areas of full wind exposure, we noted around one foot of unconsolidated snow still on the surface, available for wind transport and drifting as winds increase tonight ahead of the next storm.

There were some areas of denser wind slab above treeline that we identified and avoided. We saw no further signs of instability as we descended back into below treeline terrain.