Quick report
- Cracking
- specific
Whew, that was an intense one! During the peak of the snowfall and wind, we ventured out to investigate the distribution and sensitivity of wind slabs in terrain representative of near treeline. We found small (D1) avalanches to be easily triggered (reactive) on specific aspects, and speculated that in isolated pockets near treeline, large (D2) avalanches would be possible.
Small wind slab avalanches on specific aspects facing the north half of the compass, representative of near treeline. Shooting cracks in the new snow in places receiving wind deposition.Weather
- Air Temp
- 32
- Cloud Cover
- obscured
- Wind Loading
- intense
- Recent Snowfall
- 20
- Snow Avail For Transport
- moderate amounts
Intense blowing snow from the southwest and periods of heavy (2 inches/hour, S5) snowfall for the first hour. Visibility was minimal until 11:30. Snow slowed to a stop, along with a dramatic decrease in wind speeds around noon. Temperatures also decreased, with 0 °C measured at ~10:30 and -4 °C measured at 12:00. Obscured skies during the tour, the sun started to pop out with broken skies on the drive home.
Snowpack
~20cm height of storm snow in a location protected by the wind around 10:30 am. The new snow was being transported by strong southwest winds to northerly aspects. In places catching wind-blown snow, a new wind slab was forming on precipitation particles, down ~25cm. We were able to trigger small wind slab avalanches failing on the new/ old snow interface. Yesterday's rain built a thin crust at the top of our old snow, acting as a bed surface. With continued loading and snow available for transport, this wind slab could gain more cohesion and become larger in terms of destructive potential.
Slab: 4-finger wind-drifted snow
Weak Layer: non-persistent precipitation particles
Bed surface: "Zipper" crust from yesterday's rain
Avalanche
- Size
- D1 R1
- Type
- SS
- Aspect
- N
- Trigger
- AS
- Elevation
- 8600 ft
Small avalanches on north-facing test slopes.