Avalanche Forecast
Purcells
Avalanche danger will increase as new snow and strong winds load the snowpack. Recent storms have been very effective at triggering deeply buried weak layers and a similar pattern is expected in the coming days.
Avalanche Problem 1: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Uncertainty is best managed through conservative terrain choices at this time.
- Anticipate avalanches running full path when managing overhead hazards.
Avalanche Problem 2: Storm Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
New snow and strong west winds are expected to build fresh storm slabs over the day on Friday. Snowfall amounts are uncertain, but snow stability will be on a decreasing trend throughout the day.
Travel and Terrain Advice
- Watch for the first touchy slabs to form in the lee of ridges and wind-exposed terrain features.
- Watch for patterns of wind transport and avoid new snow that is wind loaded or stiff and slabby.
Avalanche Summary
Reports from Wednesday included observations of explosives control in the Bugaboos and surrounding area producing numerous persistent slab results from Size 2-3.5. Many of these avalanches ran on the mid-December layer buried 150-200 cm deep. Northwest through northeast aspects in the alpine were the primary targets. More limited storm slab results ran to Size 2.
A widespread natural avalanche cycle to Size 4.0 was reported on Tuesday, with larger and more frequent avalanches in the north of the region where storm snow totals were higher.
On Saturday near Kimberley, skiers remote-triggered two Size 2 avalanches near a convex roll at 2000 m elevation. The crown fracture depth was 60-70 cm, suggesting the snow ran on the mid January layer. See the MIN report for more details.
Snowpack Summary
Large differences in storm snow totals (2-32cm) were observed in the region on Monday into Tuesday. Overnight winds were strong to extreme from the southwest and temperatures spiked to -3 C at tree line.
The current snowpack is complex, with three active weak layers that we are monitoring:
60-100 cm of recent storm snow overlies a crust and/or surface hoar layer (from 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, at all elevation bands.
Deeper in the snowpack (down 70-100 cm), a persistent weak layer known as the early-January layer is 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.
Another persistent weak layer that was buried mid-December is 80 to 200 cm deep and consists of a facet/surface hoar/crust combination. It is most problematic at and below tree line and features prominently in recent avalanche reports.
Weather Forecast
Friday: Cloudy with flurries bringing 10-15 cm of new snow, continuing overnight. Strong west winds. Freezing level rising to around 1400 metres with alpine high temperatures of -5.
Saturday: Cloudy with continuing flurries bringing another 10-15 cm of new snow. Strong northwest winds. Freezing level to 1400 metres with alpine high temperatures of -6.
Sunday: Increasing cloud with flurries bringing 5-10 cm of new snow over the day. Light west winds. Freezing level near valley bottom with alpine high temperatures of -9.
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Deep weak layers are persisting in the snowpack and remain sensitive to heavy triggers. Another active storm pattern will progressively undermine stability in the coming days. Seek out simple terrain that doesn't expose you to large avalanche paths.