Avalanche Forecast

Issued: Dec 16th, 2018 5:11PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Deep Persistent Slabs and Wind Slabs.

Avalanche Canada shorton, Avalanche Canada

Triggering large avalanches remains possible, especially on wind loaded slopes.

Summary

Confidence

Moderate -

Weather Forecast

SUNDAY NIGHT: A weak front passes overnight bringing 3-10 cm of snow, strong to extreme wind from the southwest, alpine temperatures around -2 C.MONDAY: Light flurries, strong wind from the southwest, freezing level rising to 1700 m, alpine high temperatures around -5 C.TUESDAY: 5-20 cm of snow, extreme wind from the southwest, freezing level around 1700 m.WEDNESDAY: Scattered flurries with 4-8 cm of snow, strong wind from the southwest, freezing level around 1500 m.

Avalanche Summary

Explosive control produced numerous large (size 2-3) wind slab and deep persistent slab avalanches on Friday and Saturday, primarily on north and east aspects above 2000 m.Natural activity was also reported on Friday, primarily size 1-2 wind slab avalanches on east-facing lee terrain in the alpine. Some appear to have stepped down to the deep persistent weak layer near the bottom of the snowpack. See some photos of these from north of Crowsnest Pass. On Thursday, the storm snow was also very reactive to skier and snowmobilie traffic, producing widespread cracking, whumpfing, and some small avalanches.

Snowpack Summary

Strong winds have affected all open terrain, scouring windward slopes and forming wind deposits on lee slopes. Currently only 30-120 cm of snow can be found in alpine areas and much less at lower elevations.Roughly 20-30 cm of recent snow has buried old wind slabs and sun crusts. The lower snowpack has a weak structure composed of facets and crust that has been reactive to heavy triggers. Terrain features like smooth alpine bowls with variable snowpack depths are suspect for human triggering.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The weak snow in the lower snowpack could produce large avalanches. Be cautions in areas where the surface feels stiff or slabby, such as around thick wind deposits.
Back off if you encounter signs of instability like whumphing, shooting cracks or recent avalanches.Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Wind Slabs

An icon showing Wind Slabs
Recent strong winds and new snow have formed wind slabs in many exposed alpine and treeline areas.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Dec 17th, 2018 2:00PM

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