Avalanche Forecast
Issued: Feb 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Wind Slabs.
ghelgeson,
Avalanche Canada
Very large and destructive avalanches have been human triggered and released naturally over the last week. The danger is elevated below treeline to account for large avalanches that could reach valley bottom. Wind slabs remain an active problem, especially near ridge crest.
Summary
Confidence
Moderate - Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.
Weather Forecast
The trend of strong wind with dribs and drabs of precipitation is expected to continue through the forecast period.
TUESDAY NIGHT: Freezing level at valley bottom, moderate to strong northwest wind, trace of snow possible.
WEDNESDAY: Overcast, freezing level around 500 m,strong to extreme west/southwest wind, 1 to 5 cm of snow possible during the day, 2 to 6 cm possible Wednesday Night.
THURSDAY: Broken cloud cover, freezing level around 500 m, strong west/southwest wind, trace of snow possible.
FRIDAY: Overcast, freezing level around 600 m, strong to extreme southwest wind, 1 to 5 cm of snow possible.
Avalanche Summary
Since February 3rd there have been many very large destructive avalanches failing deeply on buried surface hoar and crust/facets at the bottom of the snowpack. The bulk of the activity is above treeline on north through east facing aspects, but all alpine slopes that have not yet avalanched need to be treated as suspect. A few examples of the most recent activity are reported here:
Feb 9: Very large avalanche on the Kathlyn Face near Smithers. Details/Photos here and here.
Feb 9: Large avalanche in the French Peak Complex. Details/Photos here.
Feb 9: Very large avalanche near the Pine Creek Trail. Details/Photos here.
Feb 8: Large snowmobile triggered avalanche in the Babines. Details/Photos here.
Feb 8: Very large avalanche on Mt. Elmstead above Silver King Basin Trail in the Babines. Details/Photos here.
Persistent slabs are not the only problem either, over the weekend and into Monday some touchy wind slabs were observed, check out a MIN submission here that is a great example of this kind of activity.Â
Snowpack Summary
Open terrain continues to be heavily affected by strong wind from the west which has been actively loading lee terrain features and seems to be pushing the persistent slab problem to it's breaking point. Crusts can be found on the surface up to roughly 1200 m and on open south-facing slopes.Â
Weak layers formed during cold weather in January may be part of the mechanism that has been producing the recent rash of very large avalanches. Depending on location these layers may be composed of soft facets or surface hoar and are typically buried 60-120 cm below the surface.Â
Crust/facet layers that lurk at the base of the snowpack have reactivated and have consistently been producing very large avalanches since February 3rd. The most recent signs of instability with these deeper layers have been around Smithers, Hazelton, the Kispiox and the Babines, but persistent weak layers could be a problem on slopes anywhere in the region.Â
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
- Avoid lingering or regrouping in runout zones.
Problems
Deep Persistent Slabs
Many very large, deep and destructive avalanches have been human triggered and have ran naturally since February 3rd. As visibility improves and the days grow longer there is a natural tendency to push into new terrain, but we need to recognize that places that haven't seen a lot of traffic may actually be more likely to produce these monster avalanches than places with lots of tracks. Regardless, any alpine feature that has not yet slid needs to be treated as suspect. The frequency of these avalanches seems to be picking up and this problem isn't expected to go away anytime soon.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Wind Slabs
Watch for the formation of fresh wind slabs as strong wind generally out of the west, southwest and northwest continues.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 12th, 2020 5:00PM
