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Avalanche Forecast

Mar 27th, 2015–Mar 28th, 2015
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Unusual persistent slabs continue to produce very large human triggered avalanches. See the latest forecaster blog for a more in depth look at this situation: http://bit.ly/1HHQrK2

Confidence

Fair - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Expect 5-10 cm of fresh snow by Saturday morning falling under moderate southwesterly winds with freezing levels back down to 1700 m. Continued light snow flurries are expected Saturday morning before an organized system brings another 5-15 cm overnight and 15-25 cm throughout the day on Sunday, then another 20-35 cm on Monday. Freezing levels hovering around 1800 m and strong southwesterly winds expected during the height of the storm on Sunday.

Avalanche Summary

Over the past week, very large slab avalanches have been running on the mid-March persistent weak layer. What makes this spooky is that the majority of these avalanches have been remote triggered, some from as far as 200m away. This interface remains very reactive. While it's a few days old now, the photo in this Mountain Information Network post provides a very powerful visual: https://bit.ly/1CS2Nld

Snowpack Summary

Warm temperatures and light rain have promoted settlement within the most recent recent storm snow, but the region has a very serious persistent slab problem just under the surface. A 50 to 150cm thick slab is poorly bonded to the facet/crust persistent weak layer buried mid-March. This interface has been incredibly volatile recently and remains sensitive to human triggering, especially where the slab is thinner. Recent compression tests have produced sudden planar failures at this interface. At lower elevations, rain has saturated the snowpack. The mid and lower snowpack are generally well-settled and strong.

Avalanche Problems

Persistent Slabs

High variability and severe consequences makes the mid-March persistent weakness very untrustworthy. Riders continue to remote trigger very large avalanches, even in conservative terrain.
Remote triggering is a concern, watch out for adjacent slopes.>Avoid steep high consequence terrain, convexities and areas with a thin and/or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 3 - 5