Avalanche Forecast

Issued: Feb 16th, 2015 8:00AM

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

ccampbell, Avalanche Canada

South Rockies.

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Summary

Confidence

Good

Weather Forecast

A mix of sun and cloud is for Tuesday and Wednesday with increase cloud cover expected for Thursday, but no precipitation expected. Freezing levels remain in valley bottoms for Tuesday before possible above freezing alpine temperatures on Wednesday; however, cooler temperatures expected again for Thursday, and freezing levels expected to drop to valley bottoms overnight throughout the forecast period. Generally light northwesterly winds are expected with a brief shift to moderate southwesterlies as more clouds roll in on Wednesday afternoon.

Avalanche Summary

No new avalanches reported.

Snowpack Summary

A thick supportive crust has frozen on the surface at lower elevations, with a trace amount of fresh snow on top in some places. The late January crust and surface hoar is down about 30-50 cm and recently failed with moderate effort in snowpack tests, but the failure displayed very little propensity for propagation. The mid-December buried crust layer is down about 50 cm at 2150 metres elevation and continues to react to hard forces in tests with stubborn results. The snowpack was moist down to the ground on Saturday, and is expected to re-freeze with forecast overnight temperatures. There is not much snow below 1600 metres, and a lot of bare areas below 1200 metres.

Problems

Wind Slabs

Hard wind slabs may be lurking below ridgecrest and in exposed gullies. These deep hard deposits tend to propagate over surprising distances, sometimes above trigger points into low-angled terrain on ridgecrests catching people by surprise.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Cornices

Not only a hazards in themselves, cornice falls can also act as heavy triggers for persistent slab avalanches on the 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

Unlikely - Possible

Expected Size

1 - 3

Deep Persistent Slabs

Although unlikely, these highly destructive avalanches remain possible with heavy impacts (e.g. cornice falls and surface avalanche stepping down) in the right spot (e.g. thin rocky areas). Daytime warming will also increase sensitivity.

Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar or a facet/crust layer.>Avoid steep convexities or areas with a thin or variable snowpack.>If your sled is bogging down, don’t spin the track and trigger the weak layer below.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 17th, 2015 2:00PM