Avalanche Forecast

Issued: Apr 19th, 2015 3:00PM

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

pgoddard, Avalanche Canada

Cariboos.

Danger ratings reflect conditions during the hottest parts of the day. Time your travel to take advantage of cool temperatures. Danger ratings end today, but check back for spring and summer advice.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Monday should bring warm, dry weather with light winds. The freezing level climbs to 2500 m.

Avalanche Summary

On Thursday, a naturally-triggered size 2.5 wind slab was observed on a NE aspect at 2000 m. Numerous loose wet avalanches also failed in response to warming. On Wednesday, loose wet avalanches to size 1.5 were reported below 2100 m. Widespread wind slabs were reported in the alpine and treeline. Recent whumpfing suggests human-triggered slabs may still be possible. Sun and rising temperatures are likely to lead to avalanche activity wherever the snow is warming up.

Snowpack Summary

Warm temperatures and strong sun are rapidly changing the upper snowpack. The snow surface is likely to become moist by day on most aspects and elevations. Overnight refreezing may form surface crusts. Watch out when there is no overnight refreeze: rapid weakening during the day is likely. 15 cm new snow was reported in one location on Saturday. This sits atop a crust.Down 30-40 cm is a weak layer of surface hoar and facets overlying a melt-freeze crust. In exposed alpine terrain, recent strong SW winds formed wind slabs in leeward features. Large cornices exist and may become weak with daytime warming. There are three dormant persistent weak layers that we are continuing to track. The late-March crust is down 50-70 cm and was reactive last week during the warm period. The mid-March and mid-February layers are typically down between 70 and 100 cm and have been dormant for several weeks. At the base of the snowpack, facets exist. These layers have the potential to wake up with sustained warming, a significant rain event, and/or a big cornice fall.

Problems

Loose Wet

Strong sunshine is expected to trigger loose wet avalanches on steep sun-exposed slopes. These have the potential to trigger larger slab avalanches.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Sluffs may trigger deeper instabilities.>

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Persistent Slabs

A buried interface down around 40 cm may be triggered by people or with a natural trigger like cornice fall or sunshine.

Be cautious around steep unsupported slopes and convexities.>Avoid wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Large cornices are expected to become weak with daytime warming, especially when exposed to the sun. Cornices have the potential to trigger large slab avalanches.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Apr 20th, 2015 2:00PM