Avalanche Forecast

Issued: Jan 27th, 2015 8:15AM

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

Avalanche Canada esharp, Avalanche Canada

Avalanche danger will drop as the temperature cools, however, a widespread melt-freeze crust will make for challenging riding.

Summary

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Freezing levels will drop to valley bottom overnight as a cold front moves across the province.  A ridge of high pressure will build over the coast on Wednesday resulting in clear skies and light SW winds in the interior.  A weak front will move across the province on Friday bringing isolated flurries.

Avalanche Summary

As the temperature drops I expect that avalanche activity will slow down.   The recent snow, rain, and wind were a great test of buried persistent weaknesses in the snowpack and resulted in a widespread avalanche cycle.   The mid-January surface hoar layer has been responsible for the majority of the recent avalanche activity in the region, producing numerous avalanches up to size 3.

Snowpack Summary

I suspect that freezing levels rose to about 2000m during the recent warm spell and that rain saturated the upper snowpack. At higher elevations sustained moderate to strong winds have formed widespread windslabs. Snow moist enough to make snowballs with has been found near the surface below 2200m and as deep as 80cm at lower elevations.  As the freezing level drops back a widespread melt freeze crust will form.  I suspect that at lower elevations warm moist snow may have destroyed the mid-January surface hoar layer.  Where it still exists it can be found down between 40 and 80 cm.  The midpack is broken by the mid-December surface hoar layer that is now 80 to 140cm below the surface.

Problems

Persistent Slabs

An icon showing Persistent Slabs
At upper elevations a layer of surface hoar on a crust buried 40 to 80 cm down may still be capable of producing avalanches especially in wind loaded features.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
A deeper layer of surface hoar is still producing the occasional large avalanche given a large enough trigger in the right spot. It is especially a concern on open slopes around treeline.
Conditions are greatly improved, but be mindful that deep instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 28th, 2015 2:00PM