Avalanche Forecast

Issued: Feb 3rd, 2013 9:52AM

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

mpeter, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Monday: Expect lingering clouds and light variable winds with alpine temperatures reaching -6. No precipitation.Tuesday & Wednesday: Some weak disturbances may penetrate inland to give isolated snowshowers with limited accumulations. Winds should remain light and southerly and temperatures should reach -5 each afternoon.

Avalanche Summary

Isolated windslabs up to size 2.0 have been controlled at ridgecrest and loose wet sluffing has been observed below 1200m due to the persistent warm temperatures.

Snowpack Summary

Touchy wind slabs have built on lee slopes and behind terrain features likes ribs and ridges. Up to 50 cm of new snow has buried a variety of old surfaces including old wind slabs, scoured thin slopes, crusts and surface hoar. This interface has shown isolated reactivity to rider triggering, especially around treeline and below treeline elevations. Warmer temperatures have promoted some settlement and consolidated the recent snow into slab-like characteristics. With little observations from the field it's hard to get a good handle on how widespread this layer is, so I would stress the importance of digging down to find and test weak layers. A cautious and curious approach is critical.The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

Problems

Wind Slabs

New snow and strong shifting winds has built touchy wind slabs that are likely found behind terrain breaks such as ridges and ribs. Hollow sounds and cracking snow is a good indicator of unstable snow.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls, especially at treeline and below treeline elevations.

Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Deep Persistent Slabs

A deeply buried weak layer near the base of the snowpack could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Be aware of thin areas that may propagate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 6

Valid until: Feb 4th, 2013 2:00PM