Avalanche Forecast

Issued: Jan 30th, 2015 9:27AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.

Avalanche Canada jlammers, Avalanche Canada

Don't let the clear weather on Saturday lure you into aggressive terrain. Persistent weak layers exist with the potential for large and destructive avalanches. As solar radiation increases, so will the Avalanche Danger.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday's storm system will dissipate on Saturday as a weak ridge develops. On Sunday and Monday, the ridge will flatten-out allowing for a series of pacific system to impact the region. Saturday: Generally clear skies with valley fog / Light northwest winds / Freezing level at valley bottom Sunday: Up to 10cm of new snow / Moderate southwest winds / Freezing level at valley bottom Overnight Sunday and Monday: Up to 15cm of new snow Moderate southwest winds / Freezing level at valley bottom

Avalanche Summary

There were a few close calls last weekend and into Tuesday. On Sunday in the Hankin area, a skier accidentally triggered a size 2.5 avalanche which resulted in a full burial and minor injuries. The avalanche was reported to have occurred on a wind-loaded, north-facing slope. The avalanche initially failed on the January crust/surface hoar combo, and then stepped-down to the November crust and basal facets. On the same day in the Sinclair area, a snowmobile may have been the trigger for a size 3 avalanche. The avalanche had a crown between 1 and 2 metres, and propagated up to 200 metres wide. It occurred on a wind-loaded, north-facing alpine slope and may have failed on the November crust facet combo. On Tuesday 27th, a couple of small skier-triggered avalanches were reported. One occurred on a steep roll over at lower treeline elevation and ran on the mid-January layer. The other was a small section of wind slab that pulled off a ridge line in wind affected terrain. In the wake storm loading on Friday, I would expect ongoing storm slab activity (especially in wind-exposed terrain) with the potential to trigger deeper, more destructive persistent layers.

Snowpack Summary

Moderate to heavy snowfall and strong southwest winds have built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. Below treeline, new snow accumulations may overlie a hard, re-frozen crust. A rain crust and/or surface hoar layer buried mid-January may be found at variable depths between 60- 100cm below the surface. This persistent weakness has been reactive with recent storm loading. Near the base of the snowpack is the crust-facet combination buried in November. This deep persistent weakness seems to have "woken-up" in some terrain in response to warming and heavy loading from wind and snow.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm accumulations from Friday will likely remain sensitive to human triggering. Expect increased reactivity in wind-exposed terrain. A smaller surface avalanche in motion may also trigger a larger avalanche on deeper layers.
The new snow may require several days to settle and stabilize.>Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
Persistent weak layers, buried in the middle of January, may "wake-up" in response to recent storm loading. These layers are buried up to a metre below the surface, and can surprise with nasty consequences.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Make observations and assess conditions continually as you travel.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Although less likely to trigger, recent avalanche activity suggests weak layers buried at the beginning of the winter should still be our radar. Avalanches at this interface may reach the end of their run-out zones.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 31st, 2015 2:00PM