Avalanche Forecast

Issued: Mar 19th, 2016 8:55AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Cornices, Persistent Slabs and Loose Wet.

Avalanche Canada jsmith, Avalanche Canada

Freezing levels spike on Sunday which will increase the likelihood of large natural and human triggered avalanches. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

There's a fair bit of model disagreement but freezing levels are forecasted to spike to as high as 2600m on Sunday with cloudy skies and possible flurries overnight. Monday looks cloudy with lowering freezing levels. Tuesday should be clear and cool with freezing levels dropping sharply. Light to moderate southerly winds until Monday evening when they calm down.

Avalanche Summary

On Friday, explosive control work inside a permanent closure at Kicking Horse Mountain Resort produced several size 2-3 slab avalanches which failed on both the mid and early February weak layers. This tells us that these weak layers are still alive and well even though they may be difficult to trigger in most areas. Small loose wet avalanches and failing cornices triggering slab avalanches on the late February layer would be on the forefront of my mind as I travel through the mountains this weekend.

Snowpack Summary

At ridgetop, cornices are huge and could become increasingly touchy with rising freezing levels and solar radiation. Old wind slabs still linger on lee features at treeline and in the alpine which may become more reactive with solar radiation. 40-90cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer seems variably reactive. In other words, it's still reactive to human triggers in some places while in other spots it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential to produce large avalanches. Deeper weak layers from mid-February and early January are now down 50-90cm and 70-120cm respectively. Triggering an avalanche on either of these layers has become unlikely but still has the potential to produce very large avalanches in isolated locations with a heavy trigger or significant warming.

Problems

Cornices

An icon showing Cornices
Rising freezing levels and solar radiation will promote large cornice failures which could, in turn, trigger a large avalanche on the slope below.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Persistent Slabs

An icon showing Persistent Slabs
Small loose wet avalanches and failing cornices triggering slab avalanches on the late February layer would be on the forefront of my mind as I travel through the mountains this weekend.
Use conservative route selection, stick to moderate angled terrain with low consequence.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

Loose Wet

An icon showing Loose Wet
As the sun comes out, surface avalanche conditions will include a mix of wind slabs in high elevation lee terrain, and pushy loose wet activity on steep, sun-exposed slopes. Loose wet avalanches may also trigger deep and destructive slab avalanches.
Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >Sluffs may trigger deeper instabilities.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Mar 20th, 2016 2:00PM

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