Avalanche Forecast

Issued: Apr 14th, 2013 10:02AM

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

jlammers, Avalanche Canada

Purcells.

This bulletin was produced using limited data streams, and significant variations in snowpack structure are likely to exist. If you've been traveling in the backcountry, we'd love to hear from you. Observations can be sent to forecaster@avalanche.ca.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

A ridge of high pressure is expected to develop throughout the forecast period. Overcast skies and light convective flurried are possible on Monday giving way to a mix of sun and cloud on Tuesday and Wednesday. Generally light east/northeast winds are expected each day. Daytime freezing levels are meant to climb gradually from about 1000m on Monday to about 1600m on Wednesday.

Avalanche Summary

In recent days, explosives control has produced slab avalanches to size 2 on northeast facing slopes at 2600m and higher. These slabs likely failed on the early April surface hoar. Wind slabs to size 1.5 were also triggered on north facing alpine slopes. In general, observations have become very limited.

Snowpack Summary

Light to generally moderate snow accumulations from Friday night have been shifted by variable winds into windslabs which exist at treeline and above. In some areas ongoing snowfall throughout the weekend has produced overlying soft slabs.A surface hoar interface is buried within the upper metre of the snowpack, mainly on high-elevation northerly aspects. Although it may be gaining strength, these slopes should be treated with suspicion particularly in deep snowpack areas where the overlying slab is well developed. On other slopes, recent storm snow overlies a crust.

Problems

Wind Slabs

Recent snowfall has most likely been redistributed by changing winds. Wind slabs exist on a variety of aspects at treeline and above. Wind has also formed very large and potentially unstable cornices

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

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.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Apr 15th, 2013 2:00PM