Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

We went for a tour in the rock creek drainage today with the hope of surveying the area for recent avalanche activity and for signs of instability. We found both.

• We dug in on an NW aspect at 8300’. The goals here were twofold. 1- we wanted to confirm the presence of the persistent slab problem. and two we were interested to see how it was setting up at lower elevations. We found right around a meter of right-side-up new snow from the last storm cycle which has settled relatively quickly into a cohesive slab. This new slab is resting on some well-developed, large-grained (2 mm) facets. Stability tests indicated that while this weak layer has become more difficult to trigger if a failure does occur the resulting avalanche would be at least a meter deep. (ECTX, PST 55/115 END) It is worth noting that there was some sintering within the facet layer at this location. Though the structure struck us both as concerning and directly affected our terrain choice.
• Roller balls were observed in sheltered areas BTL on southerly facing aspects and we noted surface warming along our tour even in areas with some moderate winds.
• Several large persistent slabs were visible along our tour near and above treeline One sizable avalanche was observed on the east face of Red mountain, and another crown was visible on Nevahbe Ridge. (Along my drive back to mammoth I a got better look at this crown and found a few more nearby) both of these were likely size 3 avalanches breaking within the last 24-48 hrs.
• Surface conditions along our travels today were heavily wind affected. Freshly sculpted sastrugi was present in many exposed areas and textured and wind-compressed soft snow could be found in relatively sheltered areas which provided the most pleasant descent. Our recent N winds certainly did some damage to the ski quality in the area.