Avalanche Forecast

Issued: Feb 26th, 2017 4:43PM

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

ghelgeson, Avalanche Canada

Northwest Inland.

Weak sugary snow in the bottom third of the snowpack continues to be a concern, as there is potential for large human triggered avalanches failing at this interface.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

Dribs and drabs of snow are expected for the first half of the week before the potential for a more significant system comes into play on Thursday.MONDAY: Scattered cloud cover, freezing level at valley bottom, light to moderate north/northwest wind, no significant precipitation. TUESDAY: Broken cloud cover, freezing level at valley bottom, moderate southwest wind, scattered snow showers. WEDNESDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong southwest wind, 1 to 5 cm of snow. Visit avalanche.ca/weather for a more detailed mountain weather forecast.

Avalanche Summary

On Saturday wind slabs to size 1.5 were triggered by skiers on E aspects between 1600 and 1850 m. Previously, there was a report of a size 2.5 natural avalanche in the northern part of the region. This may have happened in the last 4 days and possibly failed on a persistent weak layer buried early february on a NW aspect in the alpine.

Snowpack Summary

10 to 20 cm of storm snow accumulating in the last week has been transported by the wind, and now sits on a variety of old surface conditions including isolated wind slabs, pockets of soft snow (5 to 10 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th may exist 30 to 60 cm below the surface, but there's a fair bit of uncertainty regarding the reactivity and distribution of this layer. A stiff mid pack sits above weak sugary snow near the ground. Although possibly dormant, this basal weakness has the potential to produce very large destructive avalanches.

Problems

Deep Persistent Slabs

A lingering weakness at the bottom of the snowpack may remain sensitive to human triggering, especially in shallow snowpack areas. Surface avalanches in motion also have the potential to step down and trigger deep persistent slabs.

Avoid lingering in runout zones.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Wind Slabs

Changing wind directions Monday may form new wind slabs on south through southeast aspects. Old wind slabs may continue to linger on north through east aspects.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 27th, 2017 2:00PM