Avalanche Forecast

Issued: Mar 13th, 2016 9:08AM

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

jlammers, Avalanche Canada

Purcells.

Spring "power flurries" may produce more snowfall than forecast. Pay close attention to how much snow falls in your area and select terrain accordingly.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

On Sunday night and Monday morning expect up to 15cm of new snow and moderate southwest winds. On Tuesday and Wednesday the region should see a mix of sun and cloud and generally light northwest winds. The freezing level should hover around 1400m for the forecast period.

Avalanche Summary

Observations were extremely limited at the time of publishing this bulletin on Sunday, although evidence of a natural wind slab avalanche cycle to size 2.5 was observed in mostly northeast facing alpine terrain.

Snowpack Summary

On Saturday night, 8-15cm of new snow fell. Strong southwest winds redistributed these accumulations into touchy wind slabs at treeline and in the alpine. 35-70 cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried on February 27th, seems variably reactive. In other words, it's still really touchy in some places while in other places it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for large avalanches. Deeper weak layers from mid-February and early January are now down 50-90cm and 70-120cm respectively. Triggering an avalanche on either of these layers has become unlikely but either still has the isolated potential to produce very large avalanches with a heavy trigger or significant warming.

Problems

Wind Slabs

Snowfall amounts are uncertain for Sunday night. Spring "power flurries" may produce significant snowfall, and moderate winds may shift these accumulations into deep wind slabs in exposed lee terrain.

Be cautious as you transition into wind affected terrain.>The recent snow may now be hiding windslabs that were easily visible before the snow fell.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

A persistent weak layer continues to produce intermittent large avalanches. Although this layer is slowly becoming less likely to trigger, it has the potential to surprise with nasty consequences. I'd continue riding with a conservative mind set.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 5

Cornices

Large cornices loom over open bowls and alpine faces. Not only are massive cornice falls a hazard in themselves, but they can also act as a heavy trigger for slab avalanches on the slope below.

Stay well back from cornices.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Mar 14th, 2016 2:00PM