Wind slabs are likely to be encountered in open areas. Watch for signs of instability such as whumpfing, cracking, and recent avalanches.
The potential exists to trigger deeper weak layers, choose conservative terrain.
Wind slabs may continue to be reactive and may exist in many areas due to recent variable wind directions. They will likely be the most reactive on northerly to easterly aspects at upper elevations.
There are two main persistent weak layers of concern in the snowpack. The most recent is buried anywhere from 10-50 cm and was buried in mid-February. The next layer of concern consists of surface hoar, facets, and/or crusts, and is down 40-80 cm.
MONDAY NIGHT - Cloudy with clear periods and isolated flurries, up to 5 cm / strong west wind / alpine low temperature near -7
TUESDAY - Mainly cloudy / moderate west wind / alpine high temperature near -7 / freezing level 1500 m
WEDNESDAY - A mix of sun and cloud / moderate southwest wind / alpine high temperature near -4 / freezing level 2000 m
THURSDAY - Sunny / moderate southwest wind / alpine high temperature near -1 / freezing level 2400 m
Since the storm eased early last week, there have been daily reports of size 1-2 natural and/or human-triggered avalanches. Earlier last week, after the storm, there were also numerous size 1-2.5 explosives-triggered avalanches reported. The size and frequency of these avalanches has generally decreased each day.
There have been a few notable avalanches over the past week:
There was a large human-triggered persistent slab avalanche in the east Quartz creek area. A MIN report of this avalanche can be viewed here.
A few remotely triggered avalanches were reported in the north of the region on Wednesday that likely failed on the recently buried persistent weak layer. The MIN report can be viewed here.
There was also a size 2 wind slab avalanche in the south of the region that is suspected to have stepped down to deeper persistent weak layers last Tuesday.
Earlier in February, there were a few reports of large, sporadic avalanches on southeast aspects in the alpine, likely releasing on a layer of facets on a crust (see a photo here), and a large human-triggered avalanche on surface hoar near Quartz Creek.
10-50 cm of recent fresh snow has been redistributed by strong winds in many areas. This new snow sits on a persistent weak layer of facets that formed during the last cold snap.
Another persistent weak layer that formed in late January is now 40-80 cm deep. In the northern Purcells, this layer has been reported as a surface hoar layer at treeline and below, but a combination of facets or crusts could exist at all elevations.
The northern Purcells also have an older surface hoar layer that can still be found 60-120 cm deep at treeline. Additional weak layers may exist near the base of the snowpack. Steep, rocky areas with a shallow, or thin to thick snowpack should be considered possible trigger points.
