Avalanche Forecast

Issued: Apr 13th, 2018 3:48PM

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.

Snow and wind overnight Friday will elevate the avalanche danger.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

SATURDAY: Snow overnight Friday, accumulation 10-15cm then cloudy with flurries Saturday / Light to moderate southwest wind / Alpine temperature -3 / Freezing level 1500m SUNDAY: Cloudy with flurries, accumulation 5-10cm / Moderate north wind / Alpine temperature -2 / Freezing level 1300m MONDAY: Cloudy with isolated flurries / Light southwest wind / Alpine temperature -1 / Freezing level 1400m

Avalanche Summary

On Wednesday and Thursday there were numerous explosives triggered storm slab avalanches to size 1 and 1.5. Additionally there were explosives triggered cornice falls to size 2.

Snowpack Summary

20-25cm of new snow Friday has been redistributed by strong to extreme southwest winds. Reactive storm slabs and wind slabs built with continued snow and wind over the past 2 days. 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 to extreme southwest winds. Rain at lower elevations will weaken surface snow and increase the likelihood of loose wet avalanches.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

A weak layer buried 70 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.

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.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

1.5 - 3

Valid until: Apr 14th, 2018 2:00PM