Avalanche Forecast

Issued: Apr 15th, 2015 9:22AM

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

swerner, Avalanche Canada

Northwest Coastal.

Tricky winter conditions exist at higher elevations. Localized solar radiation, snow and winds will influence the snowpack directly. Avalanche hazard can change quickly. Use a conservative approach to terrain and watch for signs of instabilities.

Summary

Confidence

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

Weather Forecast

The current wintery weather pattern continues as a pair of fronts hits the North Coast regions bringing strong winds and more precipitation. On Thursday, 5-20 mm of precipitation is expected with moderate SW winds and freezing levels rising to 1200 m. Periods of localized solar radiation is possible.Â Friday will see a mix of sun and cloud, 3-10 mm and light ridgetop winds. The weather pattern will start to change as an upper ridge settles in for the later part of the weekend. Saturday will see mostly cloudy skies and warmer temperatures as freezing levels rise to 2000 m. For the long range, the ridge dominates the province through the weekend and will remain stationary until Wednesday bringing warm air and clear, sunny skies.

Avalanche Summary

On Tuesday, a natural cycle up to size 3 was reported from steep alpine and treeline terrain. Suspect some of these naturals are stepping down to the old interfaces buried April 9 th and mid- March. Explosive control showed numerous storm slab and wind slab avalanches up to size 2.5. These were primarily from NW-N-E aspects above 1400 m. With continued snow, rain, and strong winds natural avalanches and human triggered avalanches will likely continue on Thursday. Lower elevations which have become rain soaked and natural loose wet avalanches from steeper terrain features are expected.

Snowpack Summary

At upper elevations 25- 50 cm of recent storm snow has blanketed the region. The new snow has been redistributed by strong south-west winds into wind slabs on leeward slopes and terrain features. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) is the primary concern. The March 25th persistent surface hoar / crust layer is reportedly unreactive, however; with the new load of wind and snow this should remain on your radar as it may re-awaken, initiating very-large and destructive avalanches. Moist- rain soaked snow exists at lower elevations.

Problems

Storm Slabs

Storm slabs are touchy, especially where they sit on a buried facet, surface hoar and/ or crust interface. Strong winds have built wind slabs on leeward slopes and behind terrain features. Human triggering is likely.

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.>Avoid freshly wind loaded features.>Pay attention to overhead hazards like cornices, especially if the sun pokes out.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Additional storm snow loading on the mid- March persistent weak layer has brought it back to life. Smaller storm slab avalanches may step down to this layer, initiating large, destructive avalanches.

Be aware of the potential for large avalanches due to the presence of buried surface hoar and facets on a crust.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 16th, 2015 2:00PM