Since the lower layers of the snowpack have enough solidly frozen melt freeze to be going nowhere for a while, we were able to effectively evaluate the new snow instability inbounds at Eaglecrest today. There was 15 to 40 cm of new snow that fell very rapidly accompanied by strong SE winds last night, and it proved quite unstable.

The Eaglecrest ski patrol triggered numerous small to medium size slabs on ski cuts and with explosives. Most steep windloaded rolls seemed ready to release in the morning. Early in the afternoon, parallel tracks tests in windloaded areas on the East Bowl Chutes traverse consistently produced shooting cracks and mini-slabs. Slab tests where we scooped out the weak layer to undermine the windslab showed #2 results, fast and energetic but not taking out the surrounding snow.

We investigated and profiled a slab that was triggered by an explosive airblast on Far Chute in the East Bowl Chutes. It was unusually large for that slope, 15 to 40 cm deep, 30 m wide, and about 60 m long. We classified it as SS-AcB-R3D2-I, a soft slab intentionally artificially triggered by airblast explosive (a charge taped to a bamboo pole so it detonates above the snow surface and shocks a larger area more effectively), relative size 3 and destructive size 2, on the new snow - old snow interface.

It had a stepped fracture, picking out several weak layers within the overnight snowfall, but ultimately fractured on top of the snow that fell March 27 - 28, at 120 cm in the profile. All the new overnight snow, already changed to early rounds, sheared off. There were at least two denser, more windloaded slab layers within the new snow, sandwiched with softer layers laid down with less wind action.

The weakness seemed to be sensitive fresh soft windslab rapidly laid down on older snow, and it already showed signs of strengthening by afternoon. Two test blocks on the less windloaded west edge of the slide sheared at AK6 and RB6, both requiring multiple hard jumps and both Q2 or average shears on 36°. Both ultimately sheared on the rime and melt freeze crust at 115 cm on the profile. Our one test block on the more windloaded east edge sheared at AK2, as the tester stepped onto the block, Q1 (clean and fast shear, an indicator of stored energy in the slab) on 42° at 120 cm on the profile, the bed surface of the slide. This site was profiled as best representing what we found along the crown face.

This instability has no persistent weak layers and the bond of newer snow to the melt freeze from the last two weeks is strengthening already.The deep heavy backcountry snow should densify so travelers stay on top of it, with fresh powder dustings as showers move through this week. The snowpack should continue to strengthen rapidly. But it is possible that the snow showers forecast for the rest of the week may produce some rapid loading, windslab, or weak graupel layers that will require caution.

Snow quality on the ungroomed runs went from lighter in the morning to heavier in the afternoon, with light fresh snow on the groomed areas. We are finally out of the icy phase and into fresh snow again. Eaglecrest should have good snow all week, be sure to get out and enjoy their last two weeks of the season!