Avalanche Forecast
Purcells
Potential for human triggering of large avalanches remains high. Now is the time to remain disciplined and stick to a conservative approach towards terrain.
Avalanche Problem 1: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- If triggered storm slabs may step down to deeper layers and result in very large avalanches.
- Avoid exposure to terrain traps where the consequence of a small avalanche could be serious.
- Be very cautious as you transition into wind affected terrain, wind slabs may be deep and touchy.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Three weak layers are lurking in our snowpack that continue to produce very large avalanches. Use extreme caution in areas where weak layers may be preserved, such as in openings below treeline, and sheltered areas in the alpine and treeline.
Travel and Terrain Advice
- Be very cautious near open terrain features at lower elevations (e.g. cutblocks, gullies, cutbanks).
- Avoid open slopes and convex rolls where buried surface hoar may be preserved.
Avalanche Summary
A size 3.5 natural deep persistent slab avalanche on a north aspect at 2600m was reported northwest of Edgewater on Wednesday. The layer was suspected to be the Mid-December layer and may have also stepped-down to the November crusts. Three additional size 2 natural deep persistent slab avalanches were reported on the same mid-December layer in the same area.
Snowpack Summary
The current snowpack is complex, with three active weak layers that we are monitoring.
10-15 cm of new snow brings recent storm snow totals to 60-80 cm which overlies a crust and/or surface hoar layer (mid-January). The crust is reportedly widespread, except for possibly at high elevations on north aspects. The surface hoar is 10 to 30 mm in size and at all elevation bands. The recent snow fell with strong south winds, producing wind slabs and cornices in lee features.
Deeper in the snowpack, a persistent weak layer known as the early-January layer is buried 50 to 80 cm, present at all elevation bands, and composed of surface hoar on sheltered slopes and sun crust on steep solar aspects. Recent snowpack tests have shown sudden fracture characters with moderate loads and high propagation potential, as well as other signs of instability such as whumpfs and cracking. Another persistent weak layer that was buried mid-December is 60 to 100 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line.
A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.
Weather Forecast
FRIDAY: Mix of sun and cloud / Light southwesterly ridgetop winds / Alpine high of -11.
SATURDAY: Cloudy with flurries; 5-10 cm of new snow / Moderate southerly ridgetop winds / Alpine high of -10.
SUNDAY: 10-20cm of new snow / Moderate to strong southwesterly ridgetop winds / Freezing level rapidly rising to around 1500m.
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Up to 80 cm of recent snow has formed a slab that sits on a weak layer of surface hoar and/or a crust. Expect the slab to be especially deep and touchy in lee features due to recent strong south winds.