Avalanche Forecast

Issued: Feb 23rd, 2014 7:34AM

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

Peter, Avalanche Canada

Sea To Sky.

Sunshine and significant warming early this week could tip off a fairly widespread natural avalanche cycle.

Summary

Confidence

Fair

Weather Forecast

Synopsis: Lingering flurries are likely on Monday in the wake of a frontal system. A ridge of high pressure begins to build in resulting in clearing and drier conditions for Tuesday and Wednesday. Monday: Flurries ending early, then cloudy with sunny breaks. The freezing level is around 300 m. Winds are generally light. Tuesday: A mix of sun and cloud. The freezing level jumps as high as 2500 m with treeline temps ranging from +3 to +6. Winds are light and variable. Wednesday: A mix of sun and cloud. The freezing level jumps remains near 2500 m with treeline temps ranging from +4 to +8. Winds are light and variable.

Avalanche Summary

There was one new report of a size 2 remotely triggered slab avalanche in the Whistler backcountry. The slab depth was reported to be approximately 1.5 m deep, likely failing on a facet/crust combo. There was also a report of a size 2 accidentally skier triggered avalanche in the Blackcomb backcountry on Friday. Check out Wayne Flann's Avalanche Blog for photos of both of these incidents. Other observers in the region reported no new natural avalanches and no results with ski testing. It's likely becoming more difficult to trigger slab avalanches, but it's certainly still possible and if triggered it will likely be a deep avalanche with real potential for wide propagation.

Snowpack Summary

20-30 cm of low density snow has fallen in the past 2 days with light winds forming fresh thin wind slabs near ridge crests. The prominent mid-February weakness, which is primarily a facet/crust combo (with surface hoar in some areas), is now 70-150 cm deep depending on wind exposure. Recent snowpack tests give variable results on this layer, but some observers are still reporting sudden "pops or drops" shears and are experiencing significant whumpfing. Previous strong winds have created wind slabs in exposed lee and cross-loaded terrain. Relatively thin wind slabs have the potential to trigger the deeper mid-Feb weakness. The mid and lower snowpack are generally strong and well-settled. Basal facets and depth hoar are likely to exist in some parts of the region; however, skier triggering has become unlikely.

Problems

Persistent Slabs

A weak facet/crust combo, with surface hoar in some areas, is now down 80-150 cm and remains a concern for human triggering. This weakness shows potential for wide propagation and very large avalanches.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack. >Stick to simple terrain and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 5

Wind Slabs

Previous strong southerly winds created dense wind slabs in exposed lee terrain. These wind slabs are likely buried by low density new snow.

Use ridges or ribs to avoid pockets of wind loaded snow.>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 - 4

Valid until: Feb 24th, 2014 2:00PM