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Observation: Snowbasin Backcountry

Observation Date
2/24/2013
Observer Name
Bill Hunt
Region
Ogden
Location Name or Route
United States
Weather
Sky
Few
Wind Speed
Calm
Weather Comments
Bluebird day, very clear air across the valley.
Snow Characteristics
New Snow Depth
2'
New Snow Density
Low
Snow Surface Conditions
Powder
Snow Characteristics Comments
Above 9300 feet on Mt Allen, yesterdays wind created bizarre scouring down to hard snow I could barely kick a toe into for a few yards, alternating with 2-3 foot deep dense windslab formations. The thick windslab did not crack much or move, but did not inspire much confidence, since it was easy to get stuck in, unless cuts were higher speed. Down off the ridges in sheltered north-facing trees, powder conditions were most excellent. I heard several people state: "that was my best run of the year".
Red Flags
Red Flags
Wind Loading
Cracking
Red Flags Comments
Conditions were generally stable, but with the 30" storm total, we were being cautious. I triggered one sluff in steeper terrain that ran a hundred yards or so; and a bit of soft slab cracking was seen occasionally. One manageable soft slab pocket responded to a cut in a steeper north-facing area. Down off the ridges and away from the thicker windslab that was up high, the softer snow was fairly predictable; if the first cuts did not produce movement, then the 2nd, 3rd, and 4th skiers did not have anything move on them.
Avalanche Problem #1
Problem
Persistent Weak Layer
Trend
Same
Problem #1 Comments
The higher elevations had a great deal more wind, and the thicker snow was more difficult to cut effectively, and it seemed more unpredictable. Still, I could not get anything to move. I would not do committing cuts up there without being on belay. I did see a significant slide from Trappers Loop, through binoculars, on a southfacing slope around 8300 feet. Estimating the fracture to be 250 feet wide, perhaps 1 to 1.5 feet thick, running out of sight into a gully; at least a few hundred feet. Appears to be a natural release, possibly yesterday during the storm (did not look at this area through binocs on the drive up this morning, so I'm not sure if it was there this morning or not). This is in the first photo below.
Avalanche Problem #2
Problem
Wet Snow
Trend
Same
Problem #2 Comments
The other most significant activity I saw were skier-released sluffs on steep east-facing terrain, around 7600', which entrained some wetter sun-affected snow, and ran a few hundred feet. These were just north of Hells (sometimes called the Toilet Bowl). I first noticed these slides around 2 PM. They are in the second photo below.