Avalanche Forecast

Issued: Apr 15th, 2013 10:52AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Loose Wet and Cornices.

mpeter, Avalanche Canada

South Coast.

Danger on SOUTH and WEST facing slopes could be CONSIDERABLE in the afternoon.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Tuesday: Mostly clear skies, with a chance of clouds developing late in the day. Further inland (Coquihalla, Alison Pass) may see more cloud. Alpine temperatures should climb to -6 with freezing levels reaching 1400m. Winds should remain light from the northeast.Wednesday: Expect clouds to build through the day with alpine temperatures reaching -6 and winds turning southwesterly and increase to moderate values. Freezing levels could reach 1500m with possible isolated flurries late in the day.Thursday: Mixed skies are likely with temperatures reaching -2 and freezing levels climbing to 1600m. Expect light westerly winds and a chance of isolated flurries.

Avalanche Summary

Numerous rider triggered and isolated remote/sympathetic events have been reported in high (2400-2700m) north and northeast facing slopes up to size 2.0, all associated with preserved surface hoar.

Snowpack Summary

Recent convective snowshowers (Thursday to Sunday) have given up to 45cm of new snow at higher elevations. The surface snow is going moist on all aspects up to 2000m and continues moist into the alpine on solar aspects due to strong solar inputs. The new snow interface is predominantly crusts (sun, wind, meltfreeze) and the bonds are slowly tightening.The previous storm (Wednesday) was accompanied by moderate to strong south/southwest winds which left variable snow distribution in exposed areas near ridgetop with dense wind slabs in lee and cross-loaded features. These slabs are now buried, but may still be reactive to heavy triggers or in specific locations. Up to 75cm below the surface you will likely find a melt-freeze crust from previous sunny weather. At the same interface, spotty surface hoar is still being reported (up to 20mm!) in some high, north facing slopes. Where the surface hoar is present, consistent sudden results have been observed.Cornices are huge and have grown new tabs under the current conditions.

Problems

Wind Slabs

New windslabs have formed in immediate lee locations and the bonds with the underlying crusts may be suspect. In specific terrain avalanches have been stepping down to a persistent surface hoar layer buried last week.

Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>Be careful with wind loaded pockets.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

The surface snow will destabilize on south and west facing slopes in the afternoon if the sun is out.

The snowpack will deteriorate in the afternoon.>Plan to be off big slopes before the temperature rises and the snowpack deteriorates.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Recent snow and wind has added mass to existing cornices. Cornices can act as a large trigger to deeper weaknesses.

Be wary of slopes that are exposed to cornices overhead.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 6

Valid until: Apr 16th, 2013 2:00PM