Avalanche Forecast

Issued: Dec 9th, 2014 8:27AM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Persistent Slabs and Loose Wet.

rbuhler, Avalanche Canada

South Columbia.

The warm, wet, windy storm continues. Backcountry ski conditions are reported to be terrible and avalanche hazard remains elevated. Now is a good time for indoor activities or take your rain gear with you to your local ski hill.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The storm system continues to bring warm, wet conditions to the interior for Wednesday and Thursday. The South Columbia region can expect another 10-20mm on Wednesday and 10-20mm for Thursday. Freezing levels on both days are expected to be 2200-2500m. Alpine winds should remain strong-extreme but might start to taper off late-Thursday. On a positive note, things should start to change on Friday. Freezing levels should drop, winds should ease, and we may see new snow at higher elevations.

Avalanche Summary

A diversity of avalanche activity is expected depending on elevation. At high elevations, wind/storm slabs are expected to be the biggest concern. Reports of natural activity to size 2.5 on Tuesday. Loose wet avalanches are occurring at lower elevations where the precipitation is falling as rain. The moist new storm snow appears to be bonding well to the old surface on lower angle slopes and the slab problem does not appear to be widespread. There is still a major concern for the deeply buried weak layers where they still exist and a small avalanche or sluff may have the potential to trigger one of these layers. A human may be able to trigger these layers from a thin area like a rock outcrop.

Snowpack Summary

Reports from the Monashees of wet snow up to 2000m elevation and moist snow to around 2400m. Strong winds are loading leeward features in the alpine. Below the new storm snow may be a layer of surface hoar which was buried on Dec 5. Below around 1800m elevation and down around 40-50cm is a rain crust but it appears that the snow above it is generally well bonded. About 1m down, a weak layer of surface hoar and/or facets can be found in some locations. A thick rain crust with facets from early November is buried over 1 m down. Snowpack tests on these deep weak layers are showing slowly improving results, but in some locations these layers are still reactive and have the potential to release large slab avalanches. We may see these deep weak layers become a problem again as the storm continues to add new load.

Problems

Storm Slabs

Storm slabs will continue to build at higher elevations as the storm progresses. Strong winds will quickly reload leeward features.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Likelihood of triggering a deep weak layer is expected to increase with new storm loading and warming. Any slopes that did not avalanche during the last storm cycle should still be considered hazardous. Smaller avalanches may trigger a deep release.

Choose well supported terrain without convexities.>Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Loose Wet

Rain at lower elevations will reduce the stability of the upper snowpack and loose wet avalanches are expected in steep terrain.

Be cautious of sluffing in steep terrain.>Avoid areas with steep overhead hazard.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Valid until: Dec 10th, 2014 2:00PM