Route & General Observations
Crack of 11am departure from the Toba yurt. Standard uptrack to Manitoba summit via northwest ridge, and ski descent more or less due west. Two members of the party went for a second lap and ascended the southwest ridge. While climbing a small convexity they triggered a wind slab avalanche.
Upon returning to the parking lot, we discovered a broken window on one of our cars.
|Trigger||Skier||Avalanche Type||Hard Slab||Aspect||West|
|Elevation||3000ft||Slope Angle||40deg||Crown Depth||12in|
Two members of the party went back for a second lap approximately 3:00p and kicked off a wind slab while climbing over a wind loaded convexity near the south edge of the main Manitoba face. Slight propagation to adjacent 40 degree slope. No carry, no burial, no injuries.
Active wind loading throughout the day.
Sky: Overcast. Ceilings ~4,500'.
Temp: approx. -7 C.
Winds: Light -> Moderate over the course of the day. Strong gusts at summit around 1:00p.
Precip: Maybe some S-1. I think most of the snow in the air today was wind transport.
Below treeline: surface hoar ~ 2cm.
Treeline and above: Wind effect pretty much everywhere. High spatial variability of wind skiff, wind buff, real wind slabs, etc. For the wind slabs, there was also significant variability in the depth, strength, and "hollow-ness" of the feature.
No formal pits or stability tests. Lots of pole tests to try and find a pattern in the wind effects.