Saturday, February 4, 2017

Freeman February 4, 2017

It has been more than a week since the last posting on Mores Creek Summit blog. This past week I was giving all my attention to my Geophysics-Snow Science P.hD. Qualifying Examinations, which lasted four days. Of course, I had to spend countless hours preparing for this critical milestone between December 2016 and January 2017.

Today it was an interesting day. The day started when we arrived at Mores Creek Summit pass, and the road was blocked by snowmobilers trying to park. The parking area was not cleared of snow. We turned around and went back to Freeman Peak parking pull-out. The pull-out has not been plowed. We promptly dug a spot with our snow shovels in order to get our vehicle off the road.

We left on skins right from the vehicle. Only one lane of the road has been plowed by 8 AM, thus we used the snowy road lane to start skinning up to Freeman switchback and into Mores Creek drainage.

Air temps were above freezing level, and it was precipitating a mix of snow and rain when we started to skin up to Freeman. Above 6500 feet the precipitation was all snow. However, there was enough rain to get us pretty wet. The skiing was entertaining, but it had all the attribute of a maritime snowpack snow precipitation event. The next video provides an idea of the riding conditions.

We did not observe at Freeman's lower ridge any slab releases, but during our second run we triggered a nice whumpf at the rain/snow level. At 7000 feet a quick snow pit revealed a reactive layer buried below 40 cms with sudden collapse character (Q1). The fracture plane was located below a crust undermined by a thin layer of facets.

The new snow, about 20 cms deep, had a graupel weak layer. The new snow reacted at the graupel interface as a soft slab when we tested small steep slopes. There was another crust present beneath the new snow/graupel but it did not show any reactivity.

Due to the temps above zero, the new snow was becoming inverted (higher density at the surface, lighter density underneath.

The warm storms (free liquid water), significant loading of the snowpack with new dense (heavy) snow,  the presence of weak layers below crusts, deeply buried surface hoar (>60 cm), and shallow buried graupel have created a complicated snowpack that deserves respect. We observed today surface cracks and whumpfing. That is how nature telegraph to us that there was a slab failure. However, we did not have the steepness to make the slab slide.

The good news is that warm temps will assist with the sintering of facets layer, and depress the gradients responsible for the formation of facets. Meanwhile, ski tourers have to carefully select safe terrain for uphill travel and avoid steep terrain until the snowpack becomes less reactive.