Friday, January 31, 2014

Pilot Peak - The Last day of January 2014

Skiing was fun at Mores Creek Summit with 10-15 cm of new snow in top of a supportable rain crust.
Rain runlets at 6500 feet
The game today was to do big turns, ride fast, and do BIG turns to stay above the crust!
Big turns from my Sir Francis Bacon!
Last night's clear skies, cold temps, light winds, and water moisture left by the departing storm produced ideal conditions for the deposition of surface hoar. Also the somewhat warmer rain soaked layer below cold snow metamorphosed the new 15 cms of snow into near surface facets. Today's conditions were not like skiing soft dust on crust. Skiing the combination of a thick surface hoar coating in top of creamy near surface facets was fulfilling, particularly compared to the variable mixed conditions from last weekend.
Top of the World
The truth is that today I was suppose to do research work at MCS, and generate temperature data sets that will allow me to estimate thermal diffusivity of the various snow layer. But temperatures today were too cold to be sitting in the snowpack for +1 hour. Temps were in the -7 Deg-C range for most of the day and light winds from the NW kept the air chilly. The only setback was that I carried of instrumentation in my pack that I never used.

The only reactive layers we identified today are the buried facets from early December, which is now buried at ~ 70 cms. This weak layer continues to fail propagation saw tests with sudden planar fracture character. Compression tests support a picture where the 70 cm weak layer is hard to trigger (CTHQ1), however in one occasion a column failed during isolation (CTVQ1), and while skinning up a whumpf was triggered. This suggest that there are still isolated locations in steep terrain where it is possible to trigger a high consequence avalanche!

Conventional wisdom is that hard layers (rain or wind crusts) can isolate a weak layer and make them hard to be triggered.  This can be  a dangerous misconception. Fracture initiation can and do happen at weak spots or trigger points. Currently, the trigger points in our regional snowpack are highly variable and hard to pinpoint due to the thin and variable snowpack as well as highly faceted basal layers. Proof of that was the whumpf that Evan and I triggered later in the day as we skinned up 'Almost Top of The World', where the burly rain crust failed to "bridge' the weak layer at the random trigger point we happen to found.

Winter recreationists will notice this weekend a set of snowmobile tracks at Top of The World bowl. The bowl main line was not skiing well. Winds had transported away the new snow, but that did not discourage snowmobilers from punching it. In fact one of the snowmobiles got stuck near the bottom or a while. I hope that this is not a trend, and that such practice will NOT persist. Two weeks ago Top of The World bowl became a snowmobile playground. I like snowmobiles, and have use them to access terrain. But it is important to avoid damaging the good relationships skiers and snowmobilers enjoy at MCS for the act of few folks that might not know that they are accessing terrain that ski tourers often use. I only hope that other snowmobilers will influence their community and explain their peers that snowmobile machines allow them to get into much farther terrain not easily accessible by skiers. Ski tourers appreciate the generosity of snowmobilers that leave untouched snow slopes within 5 miles of Mores Creek Summit and Idaho 21.
Boise Mountains in the horizon from Top of The World. Notice Almost top of the World slope, and farther back the Knob Ridge.
Winter Corner is in the shade behind the Knob ridge.