Black Prospect

Quick report

Cracking

Observed

Collapsing

Observed

Skinned up Friendship Pass, 4-10" of new snow on S aspects, dropped into the N side and found 1-1.5 feet of really really really nice powder snow with no signs of instability. It is possible that with more faceted snow surfaces on northerly aspects that the new snow and old snow created a deep feel with no clear interface, that is soft and rightside up.

We had switched to bootpacking up Black Prospect when the lead trailbreaker ripped down a surprisingly cohesive storm slab, catching and carrying two of us a little ways. The third bootpacker was a safe distance below. Everyone was able to self-arrest without too much issue and with only knee/waist deep snow to dig out of. No injuries, just elevated heart rates all around. Our first run of the day had been a seemingly identical feature, same slope, same aspect, same elevation, same rocky surroundings. Other than ~1-2 feet of new snow that we were bootpacking through, there were no signs of shooting cracks, no wind effect, no recent avalanches, no cohesiveness, no obvious bed surface that we were hitting with our boots - just a bunch of right-side-up snow. We expected sluff but not a slab. Partial sun gave way to snow flurries throughout the day, then quite a bit of snow was falling during our exit. No wind, even up high. A great reminder that green avy danger doesn't necessarily mean "go".

Avalanche

Size

Aspect

Trigger

Elevation

4750 ft

Pulled down a surprisingly cohesive soft slab while bootpacking up Black Prospect. Bootpacker A was leading the charge, with Bootpacker B about 10 yards behind. Bootpacker C was further down, on a less steep part of the slope. A + B heard a massive whumpf, saw the entire snowpack around them drop suddenly, then saw the crown rip across about 30 feet above them. Bootpacker A was caught amid couch-size blocks of snow and carried 50-75 feet downslope, swimming to try to stay on top and coming to a stop right behind some rocks sticking up through the snow. B kicked and clawed his way down to the bed surface and was carried ~10 feet downslope before self-arresting on the bed surface. Despite being on a less steep part of the slope, the debris pile covered Bootpacker C up to his knees. Visibility wasn't great, so we couldn't see quite how far downhill the debris went. Everyone was OK, uninjured, and able to dig themselves out. We skiied down without further incident. Crown was 60cm tall at its highest, sidewalls were 45cm tall. Slope was 42 degrees at the crown, less on sidewalls. Bed surface looked like rounds (possibly faceted) with a normal grain size, and was 1F. Weak layer above it was 4F, with a thin inconsistent P layer right above, followed up 4F-fist of rightside-up new snow.