Avalanche Forecast
Issued: Feb 9th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Wind Slabs.
cgarritty,
Avalanche Canada
Gather observations and adopt a mindset of initial assessment in the south of the region, where a reactive storm slab problem may still be in play. Don't underestimate wind slabs elsewhere - a very large hard slab was remote triggered by a party in the north of the region Monday.
Summary
Confidence
Weather Forecast
Tuesday night: Becoming cloudy with isolated flurries bringing a trace of new snow. Light to moderate northwest winds.
Wednesday: Becoming sunny. Light to moderate north winds. Alpine high temperatures around -22.
Thursday: Sunny. Light northeast winds. Alpine high temperatures around -22.
Friday: A mix of sun and cloud. Light east or southeast winds. Alpine high temperatures around -17.
Avalanche Summary
Recent snowfall focused in the Coquihalla zone has resulted in localized storm slab activity over the weekend. Several natural and skier triggered avalanches averaging size 1-2 have been reported mostly on south aspects where they may be sitting over a slippery crust.
In the north of the region, recent avalanche activity has mainly been limited to skier triggered wind slabs size 1-1.5, however a very notable size 3 (very large) persistent slab was remotely triggered (from a distance) by a group of skiers in the McGillivray Pass area on Monday. This occurred on a southwest aspect at 2400 metres. It was described as a hard wind slab formed over a facet layer from late January.
Snowpack Summary
A stormy period from 4 to 8 February dropped approximately 60 cm of new snow in the Coquihalla, 40 cm near Allison Pass and 20 cm in the north of the region. This snow likely sits on a slippery crust on solar aspects, and possibly surface hoar elsewhere. Particularly in the Coquihalla, the new snow bonded poorly to these old surfaces and a number of avalanches were triggered on this layer. Looking forward, it is not clear whether the recent snow will bond, or whether this weak interface will remain a concern for several days. Given this uncertainty, a prudent approach would be to assume this is a suspect interface.
An earlier persistent weak layer that was buried around January 24 sits some way below the recent storm snow. This consists of facets at upper elevations, surface hoar in sheltered areas and a crust on south-facing slopes. An isolated very large avalanche on this layer in the north of the region is discussed in our avalanche summary. It averaged about 100 cm deep in that location. Whumpfs were also recently reported on this layer in the south of the region, indicating this layer might remain a concern there as well.
In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports suggest that this layer is gaining strength and it has been unreactive in recent weeks.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Wind slabs may be poorly bonded to the underlying crust.
- Be careful as you transition into wind affected terrain.
- Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
Problems
Storm Slabs
A storm slab problem may continue to exist in the south of the region, where 40-60 cm of recent snow sits on a crust on solar aspects and possibly surface hoar elsewhere. Looking forward, it is not clear whether the recent snow will bond, or whether this weak interface will remain a concern for several days. Given the uncertainty, a prudent approach would be to assume this is a suspect interface over the near term.
Loose dry sluffing may also be observed in the new snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
A wind slab problem exists in the north of the region. Wind slabs may remain reactive especially where they sit over a crust on solar aspects, at ridgetops and roll-overs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 10th, 2021 4:00PM
