Touchy cornices, building wind slabs and minimal storm slab on Hidden Peak.

We toured Hidden Peak today. Upon our arrival we encountered about 10 inches of recent storm snow at the parking area on Hwy 89. As we ascended the peak, new snow depth increased to 18 inches above about 8,000'. During the morning hours winds out of the NE were limited to ridgetop zones. As the day progressed, a light NE wind became noticeable mid slope and increased NE winds with visible plumes of blowing snow were noted along the ridgetops in the 1:15 to 1:30 pm time frame.

While we were on the ridgetop at 10:45 to 11 am, NE winds were moderate speed with signs of recent wind transport in the form of sastrugi, new cornice formations on the leeward side of the ridge, and light to moderate amounts of blowing snow. We could see several areas where the newly formed cornices over WSW aspect terrain were collapsing naturally. Upon approaching these cornices, they would break and fail with propagation about as wide as the small pockets of terrain would allow. As noted above, NE winds increased 10-20 mph as the day progressed and more blowing and drifting snow became visible along the ridgetops.

Descending the peak through NE aspect, wind protected terrain below treeline we saw only very limited evidence of storm slab instability. On one very steep rollover I was able to trigger a small storm slab and it did not propagate wider than the length of my ski. I spoke to another party on the skin track who had triggered a very similar sized storm slab while descending in similar terrain.