Avalanche Forecast

Issued: Apr 15th, 2018 4:15PM

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.

mconlan, Avalanche Canada

South Coast Inland.

More snow on Monday, with the highest amounts in the south of the region, will keep the hazard at Considerable. Observe for the bond of the snow with the underlying surface before committing into avalanche terrain.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

MONDAY: Cloudy with snowfall, accumulation 10 to 20 cm with the most in the south of the region, light to moderate southeast winds, alpine temperature -5 C, freezing level 1300 m.TUESDAY: Cloudy with light snowfall, accumulation 2 to 5 cm, light west winds, alpine temperature -6 C, freezing level 1400 m.WEDNESDAY: A mix of sun and clouds, light south winds, alpine temperature -7 C, freezing level 1300 m.

Avalanche Summary

Numerous small wind slab avalanches were triggered naturally and by skiers on Saturday, 20 to 40 cm deep and on northerly aspects in treeline and alpine terrain. These were generally running within the recent storm snow on a melt-freeze crust. Check out the MIN report here for some observations on the weekend.

Snowpack Summary

30 to 50 cm of recent snow has been redistributed by strong south winds, forming reactive wind slabs up to 1 m deep in lee terrain features. Sun, rain, and warm air temperatures on Sunday moistened the snow surface, which will freeze into a melt-freeze crust on all aspects up to at least 1800 m. Snowfall on Monday will fall on these surfaces. On ridges, cornices are reported to be large and fragile.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 50 to 100 cm. Although this layer is spotty in its distribution and avalanches haven’t been reported on it since early April, professionals are treating it seriously and avoiding terrain because of it. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.The mid and lower snowpack are well-settled and strong.

Problems

Storm Slabs

New snow may not bond well to varying snow surfaces. Slabs from the weekend have been most reactive in lee terrain features, as the snow fell with strong south winds. Watch your overhead exposure, as cornices could trigger slabs on slopes below.

Use ridges or ribs to avoid pockets of wind-loaded snow.Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.Avoid steep slopes when air temperatures are warm or when it is raining.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

Professionals are still travelling cautiously due to a weak layer buried 50 to 100 cm. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep terrain or areas with a thin or variable snowpack.Pay attention to overhead hazards like cornices, which could trigger persistent slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 16th, 2018 2:00PM