New Snow on Top of Weak Old Snow on Tamarack

We went back to Tamarack peak today to see how the weak snow handled last night's (12/8-12/9) new snow and wind. We found about 4-5 inches of new snow on top of the thin crust and 1-2 inches of snow from the storm earlier this week. All of that recent snow sits on top of the snowpack that has been steadily getting weaker since early November. This old snow has weak layers of large grained sugary snow (facets) that often cause avalanche issues. The snowpack structure was similar on all of the northelry aspects that we traveled today between the parking lot at 8600 ft to the top of Tamarack at 9890 ft.

We dug 3 different test pits and performed a variety of tests at each location. The first area was in a sheltered meadow at about 8900 ft. Here we got ECTN results and PST slab fracture results targetting the old weak layers. The second was up on the east ridge of Tamarack at about 9300 ft where some wind loading had occurred. Our results here included another ECTN and another PST slab fracture. In this spot the failure did propogate farther than at the lower location. The third test pit was near the second one but in a slightly more wind-loaded spot. Here we got an ECTP 3 between last night's new snow and the snow that fell earlier this week, an ECTN, and an RB 6 in a Rutschblock test. Taken together, all of the snowpit observations and tests indicated that there are weak layers in the snowpack, but that the snow on top of them is not much of a slab right now. More snow could overload the weaknesses that exist in the snowpack.

We also looked for signs of wind slab instability along the east ridge of Tamarack Peak. We found several test slopes that showed signs of wind-loading like ripples or small cornices above them. We only got on the test slopes that were not connected to other larger slopes since the persistent weak layer was below the surface. The wind slab on the ones we kicked was soft and cracks did not propogate very far. We did get one crack to go about 2 ft from my skis in one of wind-loaded areas. Along the ridge we also saw some signs that the winds had shifted to the north and scoured a few spots that were previously loaded.