Avalanche Forecast

Issued: Mar 11th, 2016 8:58AM

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

South Columbia.

Watch for new wind slab development on Saturday. Forecast snowfall amounts are uncertain, so pay close attention to how much snow falls in your area, and choose terrain accordingly.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Up to 12cm of new snow is forecast to fall on Saturday with another 10cm possible in the overnight period. Generally light accumulations (~5cm) are forecast for Sunday and Monday. Ridgetop winds should be moderate from the south on Saturday, becoming light on Sunday and Monday. Freezing levels should sit at about 1800m on Saturday, and then drop closer to 1500m for the rest of the forecast period.

Avalanche Summary

On Thursday there was a widespread round of natural storm slab activity (mostly in the size 2 range with some results to size 2.5) in response to new snow and strong winds. In one case a size 3 persistent slab avalanche was remotely triggered on an east-facing slope at 2230m. This points to the ongoing touchy persistent slab problem in some areas. More wind slab activity is expected with wind and snow forecast for Saturday. Although naturally triggered persistent slab avalanches are becoming less likely, human triggering remains a very real concern in some areas.

Snowpack Summary

Snowfall accumulations on Thursday were in the 10-20cm range. Strong southerly winds redistributed these accumulations into touchy wind slabs at treeline and in the alpine. 60-90cm below the surface you'll find a persistent weak layer comprised of weak surface hoar, and/or a thick crust. This layer continues to produce easy to moderate sudden planar shears in snowpack tests, and has been responsible for a number of increasingly isolated yet very large avalanches over the last few days.

Problems

Wind Slabs

New snow and wind will form new wind slabs in upper elevation lee terrain. The new snow may also be hiding older, larger wind slabs which formed on Thursday.

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 weakness lies buried up to 90cm below the surface. 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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

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.

Give cornices a wide berth when travelling on or below ridges.>Cornices become weak with daytime heating, so travel early on exposed slopes.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Mar 12th, 2016 2:00PM