Avalanche Forecast

Issued: Dec 21st, 2017 3:20PM

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

jfloyer, Avalanche Canada

Northwest Coastal.

Watch for wind slabs in unusual places, including low elevation terrain.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Kasiks (1435m):HN24 9cm; TMin -5; TMax 0; winds 30-50 NWShames (740m):6cm/6mm; TMin -5; TMax -3Bear River Ridge (1995m):Windy Upper (1490m):winds 30-60 W then NWEndgoal (370m):HN24 4cmSnowbank Mid (1065m):HN24 3cmRevision (1500m):20-35 W then NW

Avalanche Summary

Explosive control work on Tuesday and Wednesday managed to produce some large avalanches that failed on the crust buried at the end of October on north through east aspect alpine slopes in the Stewart area and north of Stewart. A natural storm avalanche cycle was observed last weekend up to size 2.5.

Snowpack Summary

The region picked up 20 to 60cm of storm snow last weekend accompanied by winds out of the southwest, west, northwest, and most recently the east. Since then, little additional snow has fallen, but cooler temperatures have kept snow dry and susceptible to being blown around by the wind. Wind slabs may rest on a melt freeze crust (reported to be 3 to 15cm thick), and there are reports there also may be surface hoar resting above this crust in sheltered locations. Below this crust the mid-pack is reported to be generally strong. You can expect to find a second prominent crust, which was buried at the end of October, 100 to 200cm below the surface. This lower layer may have associated facets, particularly in more shallow locations.

Problems

Wind Slabs

At upper elevations, northwest has been the primary wind direction. At lower elevations, easterly outflow winds are expected. Watch for wind slabs in unusual places.

Be alert to conditions that change with elevation, aspect and exposure to wind.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

This problem appears to be ongoing, particularly in areas around Stewart and to the north. Likely trigger points are in steep, rocky alpine terrain.

Be especially cautious in areas with a thin or variable snowpack.Storm slabs in motion could step down and trigger deep persistent slab avalanches.Minimize exposure to overhead avalanche terrain, carefully select genuinely safe spots to re-group.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 22nd, 2017 2:00PM