Avalanche Forecast
Issued: Jan 18th, 2020 3:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
ghelgeson,
Avalanche Canada
Wind slabs are widespread and may be found in areas you are not used to seeing them, seek out wind sheltered terrain this weekend to avoid wind slabs and find the best riding conditions.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations.
Weather Forecast
A significant storm is impacting the coast and a bit of that energy is expected to trickle inland offering dribs and drabs of precipitation through the forecast period.
SATURDAY NIGHT: Freezing level at valley bottom, moderate to strong southwest wind, 1 to 5 cm of snow.
SUNDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong south/southwest wind, 1 to 5 cm of snow possible.
MONDAY: Broken cloud cover, freezing level at valley bottom, strong west/southwest wind, 1 to 5 cm of snow possible.
TUESDAY: Scattered cloud cover, freezing level at valley bottom, moderate south/southeast wind, no significant snowfall expected.
Avalanche Summary
On Friday a small natural wind slab avalanche was observed on a southeast facing slope at 1800 m.
On Wednesday and Thursday, we received reports of natural and skier triggered wind slab avalanches size 1.5-2.5 around treeline. Crown depths were up to 1 m, and they ran on a surface hoar layer buried by the previous storm on January 10th. There's a great MIN report of wind slabs in the Hankin from Thursday here.
Reports from the Bulkley Valley Monday detail natural wind slab and persistent slab avalanche activity, size 2.5-3 on aspects lee to previous strong outflow winds. The persistent slab avalanches are suspected to be isolated incidents of avalanches running on the deep November crust.
Snowpack Summary
Extensive wind affect at all elevations. Southerly winds are forming fresh wind slabs from new snow in places that were previously scoured by northeasterly arctic outflows.
Around treeline, the old wind slabs may overly a layer of surface hoar, up to 1 m deep. This means they may remain sensitive to human triggering and resulting avalanches could be surprisingly large. Deeper in the snowpack, another couple of surface hoar layers are currently buried about 80-120 cm below the surface in sheltered areas around treeline. There have been no reports of avalanche activity associated with them for a few weeks, during which several storm slab avalanche cycles have tested their potential for step-downs.
A deep crust from mid November lurks at the base of the snowpack. A couple of recent large avalanches are suspected to have run on this layer in isolated incidents on lee and cross-loaded features high in the alpine.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
Problems
Wind Slabs
A bit of new snow and strong southwest wind are likely to form fresh wind slabs in exposed terrain through the weekend. Where previous northeast outflows formed wind slabs over surface hoar, these old wind slabs may remain sensitive to human triggering and may exceed 1 m in depth.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A deep crust from mid November lurks at the base of the snowpack. Observations about this avalanche problem are scarce but continued strong wind and warming temperatures may test the potency of this problem. Although unlikely, there is potential for some very large avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 19th, 2020 5:00PM
