Avalanche Forecast

Issued: Apr 13th, 2013 10:30AM

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

jlammers, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Sunday: Overcast skies / Light northeast winds / Freezing level at 1100mMonday: Mix of sun and clouds / Light east winds / Freezing level at 1100mTuesday: Mix of sun and cloud / Calm winds / Freezing level at 1400m

Avalanche Summary

In recent days, avalanche control has produced slab avalanches to size 2. They occurred on northeast facing slopes at 2600m and higher, and likely failed on the early April surface hoar. In general, observations have become very limited. I would expect new wind slab activity in response to new snow and wind on Friday night.

Snowpack Summary

Variable snowfall on Friday night has created new storm/wind slabs, especially near ridge top. This has added to existing storm slab and wind slab problems at alpine and treeline elevations. A surface hoar interface is buried within the upper metre of the snowpack, mainly on high-elevation northerly aspects. It is still producing moderate, sudden results in snowpack tests, and these slopes should be treated with suspicion. On other slopes, recent storm snow overlies a crust, with a variable bond. At low elevations, previously rain-soaked snow is likely to now be refrozen and strong.

Problems

Storm Slabs

Variable snowfall amounts and variable winds have created new storm slabs, especially near ridge top and on slopes in the lee of the wind.

Avoid travelling in areas that have been reverse loaded by winds.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Persistent Slabs

A layer of surface hoar is buried about a metre down, mainly on high northerly aspects. A surface avalanche stepping down, cornice fall, or the weight of a person from a thin-spot trigger point could trigger it.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 6

Valid until: Apr 14th, 2013 2:00PM