Avalanche Forecast

Issued: Mar 18th, 2016 10:18AM

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

Rising freezing levels over the weekend 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

High

Weather Forecast

Another sunny day forecasted for Saturday with freezing levels rising to around 2000m. Cloudy skies are expected to return either Saturday evening or Sunday morning, but the exact timing of this is uncertain.  If it's cloudy Saturday night, the hazard will increase on Sunday due to lack of "crust recovery". On Sunday, freezing levels rise sharply to as high as 2500m with possible flurries in the afternoon. The unstable weather continues into Monday. Generally light southerly ridgetop winds are forecasted throughout the period.

Avalanche Summary

On Thursday, a skier triggered a size 2 slab avalanche on a north aspect at 2400m.  The weak layer buried in late February was the likely culprit of this avalanche.  Additionally, several naturally triggered size 2 slab avalanches were reported on a variety of aspects in the alpine. They generally started as smaller loose wet avalanches triggered by solar radiation that then stepped down to the persistent weak layer that was buried late February. Solar radiation and increasing freezing levels will be the main driver of natural avalanche activity in the coming days.

Snowpack Summary

At ridgetop, cornices are huge and could become increasingly touchy with forecast solar radiation. Expect old wind slabs on lee features at treeline and in the alpine to become more reactive with solar radiation. Sunny skies have likely promoted a melt-freeze cycle on sun-exposed slopes. 60-110cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried in late February, seems variably reactive. In other words, it's still touchy in some places while in other places 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 very large avalanches. Below this interface, the snowpack is generally strong and well-settled.

Problems

Cornices

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Persistent Slabs

An icon showing Persistent Slabs
The late February layer is becoming less likely to trigger, but it continues to surprise riders with large avalanches. I'd aim for well-supported slopes without convexities, and be increasingly cautious as freezing levels increase.
Choose well supported terrain without convexities.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

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.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Sluffs may trigger deeper instabilities.>Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Mar 19th, 2016 2:00PM