Avalanche Forecast

Issued: Apr 12th, 2018 3:57PM

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

Sea To Sky.

Precipitation is coming Friday and will intensify in the afternoon and evening. This will be accompanied by strong southwest wind. As the precipitation accumulates, the avalanche danger will rise.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

FRIDAY: Snow, accumulation 25-35cm / Strong southwest wind / Alpine temperature -2 / Freezing level 1400 m SATURDAY: Cloudy with flurries and some sunny breaks/ Moderate to strong southwest wind / Alpine temperature -4 / Freezing level 1400 m SUNDAY: Flurries / Light west wind / Alpine temperature 2 / Freezing level 1600m

Avalanche Summary

On Wednesday there were several explosives triggered storm slab avalanches to size 1 and 1.5. On Tuesday, limited alpine observations existed due to weather. Above 1900 m skier triggered isolated slabs up to size 1 were easily triggered. At lower elevations small loose wet natural avalanche activity occurred. Avalanche activity will be on the rise with the incoming storm on Friday leading into Saturday. Its still winter out there!

Snowpack Summary

Warm temperatures and rain have moistened the snow surface on all aspects and at all elevations with new snow accumulations in the alpine up to 15 cm and building. Reactive storm slabs and wind slabs are building with continued snow and strong southwest winds. Ridgelines are heavily corniced and if they fail they would act as a trigger on the slope below. A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 120 cm down. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. Below this, the snowpack is well-settled and strong.

Problems

Storm Slabs

Storm slabs are building at upper elevations. Slabs will be thicker in lee features, as the snow will fall with strong southwest winds. Rain at lower elevations will weaken surface snow and increase the likelihood of loose wet avalanches.

Extra caution needed around cornices with current conditions.Minimize exposure during periods of heavy loading from new snow and wind.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

A weak layer buried 60 to 90 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.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.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

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