Avalanche Forecast

Issued: Mar 1st, 2018 4:32PM

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

mbender, Avalanche Canada

North Columbia.

Think wind slabs on lee slopes and a persistent slab that seems to be "waking up" on southerly slopes.

Summary

Confidence

Moderate - Freezing levels are uncertain on Friday

Weather Forecast

FRIDAY: Cloudy with isolated flurries / Light southeast wind / Alpine temperature -7 / Freezing level 1000m SATURDAY: Cloudy with isolated flurries / Light southeast wind / Alpine temperature -8 / Freezing level 900m SUNDAY: Mix of sun and cloud / Light southeast wind / Alpine temperature -12 / Freezing level 500m

Avalanche Summary

On Wednesday a size 2 remotely triggered (from a distance of 10m) persistent slab avalanche was reported to run on surface hoar sitting on a crust that was buried mid February. This was on a southwest aspect at 1800m. Other recent avalanche activity has consisted of mainly wind slabs and loose dry in the size 1-1.5 range but up to size 2. These were either naturally occurring or intentionally triggered. More interesting avalanches included a re-loaded bed surface where an avalanche previously released on the Nov crust and the "newly awoken" Feb 14 crust found on solar aspects. Deep persistent avalanche activity has become less frequent over the past week.

Snowpack Summary

Around 40 to 60 cm of recent storm snow is being redistributed into deeper, reactive slabs in wind-exposed terrain. Below this is a layer buried mid-February that presents as a sun crust on solar aspects, and spotty surface hoar on sheltered slopes. This layer looks most concerning on on solar aspects where it's associated with with small facets or surface hoar above.There are several deeper layers in the mid-pack that have shown signs of improving but remain on the radar as having a low probability of triggering yet a high consequence avalanche if they are triggered. We're talking about surface hoar layer buried back in December and January. Near the base of the snowpack is a November crust combined with loose sugary snow. These layers may "wake-up" with strong inputs such as sustained warming, sustained snowfall, large triggers (e.g. cornice fall, smaller avalanches coming down from above); human triggering is also possible in shallow snowpack areas with variable snow depth and convoluted terrain.

Problems

Wind Slabs

Shifting wind means there may be old buried wind slabs in places you don't expect them i.e. reverse loading, however the most recent wind has been slowing from a southerly direction.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.Be cautious as you transition into wind affected terrain.Use caution on steeper open slopes and convex rolls in wind sheltered areas.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Persistent Slabs

An interface buried up to 70cm deep has "woken-up" with recent snow loading, and a few large avalanches have been triggered easily. Observations have been limited, but this problem seems most reactive in south-facing terrain where buried crusts exist

Watch convoluted terrain with variable snowpack depth and multiple trigger points.Make observations and assess conditions continually as you travel.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

Aspects: North, North East, East, South East, South.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Mar 2nd, 2018 2:00PM