Stiff Wind Slabs, Recent Snow, and Surface Hoar on Castle

On the way up the Castle Peak Rd, we moved off the beaten track several times to see how things felt. We found a few inches of soft snow on top of much more dense supportable snow on top of a rain crust. Poking into the snowpack with our poles, we found softer layers a few feet below the surface, but they did not feel as weak as in other areas around the forecast area. Overall the snowpack felt deeper and more consolidated with these general obs. For us, those general obs did not constitute enough solid information to venture into steeper terrain, especially with a potential persistent slab problem. So we stuck to lower angle terrain as we ascended to the ridge.

Once we got to the ridge, we found signs of blowing snow all around us like ripples and scoured areas on the ridge and small cornices overhanging stiff slabs of drifted snow on the leeward (NW,N, E, SE) aspects. We kicked some of the small cornices onto small test slopes below them and stomped on the small test slopes but did not trigger any wind slab failures. The wind increased as we ascended and snow conditions on the ridge became more variable. We found a more loaded test slope and dug into it. Our quick pit and tests did not show any signs of instability (ECTX @ 39.3647, -120.3595 on a NW aspect @ 8280 ft). At this point, we decided to abandon the ridge and traverse low across the NW trees of Castle to avoid crossing the steeper slopes higher on the peak and to avoid the variable snow surfaces on the ridge. 

In the shelter of the trees, snow conditions proved much easier for traveling with one exception: chunks of rime that had fallen off the trees covered the snow surface directly under some trees. We kept probing for the persistent weak layers in the snowpack. It felt similar to how it felt at the lower elevations. We stopped to dig a full pit on a low angle slope at an opening. The snowpit data and tests confirmed what we had been feeling. The Dec 11 facets were about 3 ft below the surface and they showed signs of gaining strength (see pit profile for details).

We continued up on low angle slopes in the trees to the ridge between Castle and Basin where we could safely look into the N bowl of Castle. We could see obvious signs of wind loading like cornices above the slopes and drifts on the slopes, but we did not see any recent avalanche activity from our vantage point (we could not see all of the bowl). We knew that stability can be variable and unpredictable when persistent slabs are involved and that the consequences of a persistent slab avalanche could dire especially in complex terrain like the N bowl of Castle. As planned, we turned around and descended the low-angle NW trees where snow conditions were nice and consistent and we did not incur the extra risk of persistent problems on steeper terrain. Down in Round Meadow, we found widespread surface hoar.