Avalanche Forecast

Issued: Mar 25th, 2017 4:15PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs, Persistent Slabs and Cornices.

shorton, Avalanche Canada

North Columbia.

Remember snow can lose strength very quickly on sun exposed slopes. Watch for overhead hazards and stick to supported terrain with low consequence.

Summary

Confidence

High -

Weather Forecast

SUNDAY: Sunny in the morning then clouding over around noon, light south wind, alpine temperature around -5 C.MONDAY: Isolated flurries with 3-5 cm of snow, light southwest wind, alpine temperature around -5 C.TUESDAY: Scattered flurries with another 2-4 cm, moderate southwest wind, alpine temperature around -5 C.

Avalanche Summary

On Friday, small storm slabs were reactive to skier traffic on convex and wind loaded northerly aspects. Numerous size 1 avalanches were triggered in the top 20-30 cm of snow. Cornice failures were reported on a daily basis earlier in the week, with about one per day triggering a large slab on weak layers up to 2 m deep.On Sunday, morning sun is a potential trigger for cornice falls and deeper weak layers. Read the forecasters blog (here) for advice on how to manage this low probability, high consequence scenario and check out the accompanying photos (here). Also expect the recent snow to settle into a slab that will be most reactive at higher elevations, especially in wind loaded terrain and on steep convexities.

Snowpack Summary

20-50 cm of new snow overlies a rain crust below around 2000 m or a sun crust on solar aspects at higher elevations. Alpine wind has recently been strong mainly from south through west directions and has loaded leeward slopes in exposed terrain at treeline and in the alpine. Large cornices are also reported on northerly aspects in the alpine. The rain crust which formed last week is now down 50-60 cm and generally seems to be well bonded to the surrounding snow. The February weak layers are down 120-150 cm and woke up during the recent storm cycle with many avalanches stepping down. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have stepped down to these layers recently resulting in very large avalanches.

Problems

Storm Slabs

Ongoing incremental loading is building slabs which may sit over a rain crust or sun crust. These slabs are most reactive in wind loaded terrain.

Use caution on steep open slopes and convex rollsBe alert to conditions that change with elevation.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Sustained sun exposure or heavy triggers like a cornice falling could trigger deep, destructive avalanches on buried weak layers.

Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.If triggered, storm slabs or cornices may step down to deeper layers resulting in very avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Cornices

Cornices on northerly aspects are large and may become weak when hit by the sun.

Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.Give cornices a wide berth when traveling on ridges.Cornices become weak with daytime heating.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 26th, 2017 2:00PM