Avalanche Forecast

Arctic air brings cold temperatures, wind and little chance of snow until Friday.

TUESDAY NIGHT: Cloudy, with light NW winds. Scattered flurries. Freezing level at valley bottom. 

WEDNESDAY: A mix of sun and cloud, moderate NW winds. Freezing level at valley bottom. Alpine high -15.

THURSDAY: Cloudy, moderate NW winds. Freezing level at valley bottom. Alpine high -10. 

FRIDAY: Cloudy, with up to 5 cm expected. Moderate to strong SW winds. Freezing level around 500 m. Alpine high of -5. 

Slabs were triggered naturally and by skiers/riders to size 1.5 over the last 4 days. Activity was limited to higher elevations on east aspects, where wind loaded terrain features. Small loose dry avalanches have also been reported, running on the buried surface hoar layer. 

Avalanche activity on the early-December facet/crust weak layer described in the snowpack summary has been sporadic over the past few weeks. Prior to this most recent drought, we were tending to see reports of avalanches on this layer every few days. Most of the avalanches occurred at elevations around 2000 m. Possible natural triggers include daytime warming, warming from the sun, cornice falls, or smaller avalanches stepping down. Human triggering is most likely in steep, rocky slopes with a shallow or thin-to-thick snowpack.

At lower elevations, around 20cm of storm snow sits over a thick melt freeze crust. In sheltered terrain, a widespread layer of surface hoar sits immediately above the crust, typically 5-15mm.

At higher elevations the storm snow is being redistributed by moderate to strong westerly winds, over a previously wind affected snow surface. A thin melt freeze crust extends into the alpine on solar aspects. This crust may sit on the surface in exposed terrain, or below wind deposited snow in sheltered features. 

Several surface hoar layers are buried in the upper snowpack 30-60cm deep included the January 11 crust/surface hoar interface. 

The most notable layer of concern in the snowpack is a facet/crust layer that formed in early December and ranges in depth between 80 cm along the shallower eastern Purcells and up to 150 cm in the west. This recent blog post details this interface. Read up on why it is expected to continue to create problems for the rest of the season. 

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
• Conditions may have improved, but be mindful that deep instabilities are still present.