Choose terrain carefully, and investigate for signs of instability and buried layers of weak surface hoar.
The weight of a rider could cause a surprisingly large avalanche on this layer.
This problem mostly refers to a weak layer buried in early December, but a layer buried mid December could be active around Pine Pass, where storm snow is deeper. Surface hoar is most likely to be preserved in areas sheltered from the wind.
Friday night, 5-20 cm of storm snow arrived with moderate to strong southwest wind, likely forming thin, reactive pockets of windslab over old, hard surfaces. South and west-facing slopes in the alpine and at treeline that are exposed to the wind have been scoured to hard, old snow surfaces.
A concerning layer of weak, feathery surface hoar crystals can be found around 30-50 cm deep.
The midpack may contain a few frozen crusts, and the lower snowpack is generally faceted. Average snowpack depths at treeline range from 50 to 100 cm.
No new avalanches were reported on Saturday before 4pm. This recent MIN post from our North Rockies field team talks about signs of instability due to buried surface hoar layers, and how that influenced their choice of riding terrain in the Hasler area.
If you go out in the backcountry, please consider sharing your observations on the Mountain Information Network (MIN).
Temperatures may be colder west of Pine Pass.
Saturday Night
Mostly clear. No new snow expected. Moderate west or northwest ridgetop wind. Treeline low around -7°C. Freezing level at valley bottom.
Sunday
Mostly cloudy. Possible trace of snow expected. Strong to extreme southwest ridgetop wind. Treeline temperature around -6°C. Freezing level around 1000m.
Monday
Mostly cloudy. 2-5 cm of snow expected. Wind decreasing to light southeast by the end of the day. Treeline temperature around -4°C. Freezing level falling to valley bottom by end of day.
Tuesday
Mostly cloudy. 5-10 cm of snow expected. Moderate southwest ridgetop wind. Treeline temperature around -4°C. Possible temperature inversion.
More details can be found in the Mountain Weather Forecast.
