Avalanche Forecast

Issued: Feb 7th, 2015 7:59AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Loose Wet and Deep Persistent Slabs.

jlammers, Avalanche Canada

South Rockies.

The storm may have tapered-off, but the snowpack will need time to adjust to the heavy load of the new snow, and water saturation at lower elevations. Conservative terrain selection remains critical.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

The pineapple express will persist for Sunday and Monday, but it will lose much of its "punch". A warm, dry ridge will then build for Tuesday. Sunday: Light precipitation / Strong southwest winds / Freezing level at 2000m Monday: 5-10cm of snow at higher elevations / Moderate to strong southwest winds / Freezing level at valley bottom with a chance of an inversion Monday: A mix of sun and cloud / Light northwest winds / Freezing level at valley bottom with a chance of an inversion

Avalanche Summary

Observations have been extremely limited in recent days. That said, several storm slab avalanches to size 2.5 were reported in the south of the region on Friday. I get the feeling this was just the tip of the iceberg. Triggering storm slabs will remain a concern at higher elevations for the next few days. At lower elevations where precipitation has fallen as rain, I would expect ongoing loose wet and wet slab avalanche activity.

Snowpack Summary

In the alpine, up to 50cm of moist, dense snow overlies a touchy crust/surface hoar layer which was formed in late January. These new snow accumulations have been pushed by strong southwest winds into much deeper deposits in upper elevation lee terrain. At lower elevations very heavy rain has saturated the snowpack. I'm sure cornices are large and fragile.The sustained rain should continue to break down the late January crust, increasing the possibility of avalanches stepping down to deeper weak layers. The mid-December crust/facet/surface hoar combo is found down 50 - 95 cm. Rain and/or heavy storm loading could spark renewed activity at this interface with the potential for very large avalanches.

Problems

Storm Slabs

Deep, dense and destructive storm slabs have formed at upper elevations. Human triggering will remain a concern, especially due to a recently buried crust/ surface hoar layer.

Be alert to conditions that change with elevation.>The new snow will require several days to settle and stabilize.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 4

Loose Wet

Heavy rain and forecast warm temperatures will promote ongoing loose wet avalanche activity. Loose wet avalanches can be pushy and entrain mass quickly. Use extra caution in steep gullies.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of wet sluffing in steep terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

The snowpack is rain-soaked and weak. This increases the likelihood of avalanches failing on deeply buried persistent weak crystals which formed in December. Although less likely, avalanches at this interface would be destructive in nature.

Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar or a facet/crust layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 8th, 2015 2:00PM