Avalanche Forecast

Issued: Feb 1st, 2013 9:25AM

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

swerner, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Saturday: Overcast with no significant precipitation expected. Light amounts in the Northern part of the region. Alpine temperatures near zero degrees with freezing levels hovering around 1000-1300 m. Ridgetop winds will blow moderate from the South.Sunday: The brunt of the frontal system will take effect, bringing moderate precipitation accompanied by strong SW ridgetop winds. Alpine temperatures near -4.0 and freezing levels gradually falling to 800 m. Monday: Cloudy skies with light precipitation. Ridgetop winds will blow light from the South. Alpine temperatures dropping to -7.0 with freezing levels lowering to 400 m.

Avalanche Summary

On Friday, several natural loose, slab and glide avalanches were spotted from a heli flight up to size 2.5. I suspect loose wet avalanches continued in below treeline elevations.

Snowpack Summary

Touchy wind slabs are most likely found on NE-W slopes and behind terrain features like ridges and ribs. Warmer temperatures have promoted settlement and consolidated the recent storm snow into slab-like characteristics. Lingering beneath (down 50-80 cm) sits a persistent weakness comprising of surface hoar, facets, and /or a crust. Recent test done on these layers are producing hard results with sudden and resistant planar results. Keep these layers on your radar in regards to reactivity and sensitivity until we get through the warming period. Snow may become moist or wet at treeline and below and become unstable.The mid and lower snowpack is generally well settled and strong, although basal facets remain a concern in the northern part of the region.

Problems

Wind Slabs

Strong shifting winds have built touchy wind slabs that are likely found behind terrain breaks such as ridges and ribs and on lee slopes. Wind slabs may be easily triggered under the weight of a person and/or a machine.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>Assess start zones carefully and use safe travel techniques.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

Over the past week up to meter of new snow has fallen on a crust/facet/surface hoar interface. This interface may be found most reactive in sheltered areas over convex rolls or steep terrain. Dig down and see how reactive it is in your riding area.

Whumpfing is direct evidence of a buried instability.>Avoid slopes that are showing signs of instability due to warming.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Feb 2nd, 2013 2:00PM