4 Season Outdoor Adventure Guides in Hakuba Japan

Archive for the 'Avalanche Skills Training' Category

AST 1 Avalanche Course

Published by evergreen on February 20, 2012 under Avalanche Skills Training, General

The crew moves out.

Dave gets major shooting cracks on another test slope as the crew looks on.

Everyone tries some quick tests on a small slope with known weakness.

Dave in the snowpit.

Dave finds an easily-triggered test slope, releasing on the faceted melt form crust from the last thaw.

Another natural release from the cycle of yesterday and the night before; shallow enough to likely have run on the density difference 30 cm down rather than the faceted melt form crust 170 cm down, but running full-length on its path.

The crew works on snow tests. The uppermost prominent layer was a density difference some 30 cm down, formed when the last storm went from fluffy unrimed stellar crystals to small plates and lightly rimed broken crystal fragments as the temperature dropped and the wind increased. The deeper layer of concern is the faceted melt form crust from the last thaw event and subsequent cold weather. It is still triggerable at some 170 cm depth, and propagates easily and cleanly as a Q1, sudden collapse, or sudden planar break. These layers are highly persistent and unpredictable, lulling people into a false sense of security until they release massively when the wrong spot is hit. Take care out there; just because people get away with riding big slopes with this weakness does not mean it is in any way “safe”!

AST II Course still continues…

Published by evergreen on February 14, 2012 under Avalanche Skills Training, General

Tom loads a Compression Test with moderate blows from the elbow.

Tom checks the results. One of our CT blocks fractured on the deep weak layer; the other did not. Once fractured, it was a Q1 or sudden planar shear; indicative of problems even though it took quite a few blows for the deep weakness to let go. Fracture on these shallower weak layers could trigger the deep one.

Tom and Chris pull a chunk of windslab out of the access "chimney" between their Compression Test blocks

Chris loads an Extended Column Test with hard blows from the shoulder. With our faceted melt form crust some 160 cm down at our test site, ordinary blows did not give us propagation, but trimming the column down and loading it with a standing person resulted in complete propagation. Tests on deep slabs often yield inaccurate and conflicting results.

Andrew jumps on the AK Block. With a hard slab, low slope angle, and deep weak layer, this one did not release on the deep weakness. But that is common with faceted melt form weak layers. They often appear strong in tests but let go massively when a rider hits their sweet spot.

Cinnamon Roll Snow Version

Published by evergreen on February 7, 2012 under Avalanche Reports, Avalanche Skills Training, General

“Cinnamon rolls” were common as warm weather arrived in the Tsugaike backcountry just as we finished up the first weekend of our AST avalanche course today. We’re due for one day of warm wet air from Southeast Asia to pass through; by Tuesday evening cold air moves in behind the departing weather system and brings the usual Hakuba snowfall back. Photo and commentary by Bill Glude.