Avalanche Forecast

Issued: Apr 12th, 2018 3:49PM

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.

mbender, Avalanche Canada

South Coast Inland.

Precipitation is forecast to start Friday morning and will intensify in the afternoon and evening. This will be accompanied by strong southwest wind. Avalanche danger will rise as the precipitation accumulates.

Summary

Confidence

Moderate - Timing of incoming weather systems is uncertain on Friday

Weather Forecast

FRIDAY:Â Snow, accumulation 15-25cm in the north and 25-45cm in the south / Strong southwest wind / Alpine temperature -2 / Freezing level 1300 m SATURDAY: Periods of snow, accumulation trace to 5cm in the north and 15-20cm in the southÂ / Moderate to strong southwest wind / Alpine temperature -1 / Freezing level 1400 m SUNDAY: Flurries / Light to moderate west wind / Alpine temperature 0 / Freezing level 1600m

Avalanche Summary

On Monday, a MIN report from the Duffy Lake area showed a skier accidental size 2 storm slab from a north aspect at 2700 m. Please check out the report here. No new observations on Tuesday or Wednesday, however, alpine observations seemed limited due to the weather. Expect the avalanche activity to increase through the forecast period with new snow and wind.

Snowpack Summary

5-15 cm of new snow overlies moist snow surfaces and is accumulating. At higher elevations, this overlies wind slabs formed from last weekends snow that fell with strong southwesterly winds. On ridges, cornices are reported to be large and fragile. At low elevations below treeline, recent rain has created moist or wet snow conditions.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. This layer is spotty in its distribution. 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

Forecast precipitation will come in as snow at upper elevations and rain at lower. Storm slabs will become more reactive as new snow amounts accumulate. Expect loose wet avalanches where the precipitation falls as rain or as a mix of rain and snow.

Use ridges or ribs to avoid pockets of wind-loaded snow.Watch for signs of instability such as whumpfing, or cracking. Minimize exposure to avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer buried 50 to 100 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

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

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 13th, 2018 2:00PM