Avalanche Forecast

Issued: Apr 18th, 2018 4:18PM

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

cgarritty, Avalanche Canada

Cariboos.

Forecast sunshine and warming will increase the likelihood of triggering in a wide range of avalanche problems on Thursday. Expect stability to deteriorate over the day.

Summary

Confidence

High -

Weather Forecast

Thursday: Mainly sunny with cloud increasing over the day. Moderate south winds. Freezing level rising to 2000 metres with alpine high temperatures around -2. Weak overnight cooling.Friday: Cloudy with isolated flurries and a trace of new snow, increasing overnight. Moderate south winds. Freezing level to 1900 metres with alpine high temperatures around -3.Saturday: Cloudy with continuing flurries bringing 5-10 cm of new snow. Light to moderate southwest winds. Freezing level to 1700 metres with alpine high temperatures around -4.

Avalanche Summary

Reports from Tuesday included observations of several large (size 2) wind slabs that released naturally as a result of recent strong winds.Observations were hindered by poor visibility on Monday.Reports from Sunday and late last week showed a pattern of heightened cornice failure activity, with several cornice releases triggering large persistent slabs and wind slabs.Looking forward, a trend toward clearing skies and warming temperatures will be increasing chances of loose wet avalanche activity as well as testing the strength of storm slabs and wind slabs formed in the wake of recent snowfall and wind events.

Snowpack Summary

About 50 cm of recent storm snow covers a supportive crust on all aspects to at least 2100 m (and possibly higher on south aspects). Shifting strong southwest and north winds pressed and redistributed the most recent accumulations into new wind slabs on a range of aspects on Monday.Within the upper snowpack there are now several different crusts with the shallowest of these (down about 25 cm) remaining a concern as the uppermost layer of storm snow settles and bonds to it.There is some lingering concern around the mid-March persistent weak Layer in the alpine where it is found 100 to 150 cm below the surface. This buried crust/surface hoar interface is still capable of producing large avalanches if it is triggered (think step-down from a surface avalanche or a cornice collapse).Deeper persistent weak layers from December and January may be starting to become reactive to very large triggers. A recent cornice collapse is believe to have initiated a slab release on an early season layer, 300 cm deep.

Problems

Loose Wet

Rising freezing levels and increasing sunshine will destabilize surface snow and promote loose wet avalanches in steeper terrain. Loose snow releases may occur naturally or with a human trigger.

Use extra caution on slopes if the snow is moist or wet.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.Manage your sluff and be extra cautious where long slopes allow for more snow entrainment.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 2.5

Cornices

Several large cornice failures have been reported in recent days. Large cornice collapses have the potential to trigger a deep weak layer near the base of the snowpack, which would result in a very large and destructive avalanche.

Cornices weaken with sun and daytime heating. Minimize your exposure to large cornices overhead.Give cornices a wide berth when traveling on or below ridges.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Storm Slabs

The strength of storm and wind slabs formed after the last snowfall will be tested by warming on Thursday. The greatest caution is needed around steep or wind loaded slopes as well as sun-affected areas where slabs may have formed over a crust.

Watch for signs of instability such as shooting cracks or recent avalanches.Exercise increased caution around south aspects where new snow may have formed a slab over crust.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 19th, 2018 2:00PM