Avalanche Forecast

Issued: Jan 31st, 2019 4:47PM

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

Avalanche Canada cgarritty, Avalanche Canada

Stability will deteriorate over the day as new snow stacks up. There's a good chance this dump will be enough to bring our buried weak layer back to life. Consider the danger to be HIGH in areas that receive over 30 cm of new snow.

Summary

Confidence

High -

Weather Forecast

Thursday night: Cloudy with continuing flurries bringing 10-15 cm of new snow. Moderate to strong southwest winds.Friday: Cloudy with continuing flurries bringing around 10 cm of new snow and new snow totals to 25-30 cm. Snowfall continuing overnight. Light to moderate southwest winds. Alpine high temperatures around -6.Saturday: Mainly cloudy with easing flurries bringing up to 5 cm of new snow and new snow totals to 40-50 cm. Light winds shifting from southwest to northeast. Alpine high temperatures around -12 and falling over the day.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light northeast winds. Alpine high temperatures around -26.

Avalanche Summary

Reports from the region on Wednesday included one observation of a small remote (from a skier at a distance) triggered wind slab occurring in the lee of ridgecrest on a north aspect at 1850 metres. On Tuesday reported avalanche activity was limited to a size 2 cornice failure above a southeast facing slope at 2500 m. No new avalanche activity reported on Monday. On Sunday cornice failures to size 1.5 were observed on north through east facing terrain around 2000 m. Small natural wind slab avalanches to size 1 were reported on east and northeast facing terrain between 2000 and 2300 m.On Saturday a skier triggered a small persistent slab avalanche on an east facing feature at 2000 m, failing on the mid-January surface hoar.

Snowpack Summary

New snow has begun to bury the previous surface, which consists mainly of wind-affected surfaces at higher elevations with a new layer of surface hoar present at lower elevations and in some protected areas closer to treeline. Sun crust is being buried on steep, south-facing aspects. Areas where sun crust and surface hoar coexist could produce particularly touchy slabs as new snow accumulates. 15 to 45 cm of older storm snow continues to consolidate above the mid-January persistent weak layer (PWL). This PWL is made up of large surface hoar that is most prevalent at and below treeline, with enhanced reactivity noted between 1500 and 1800 m. On steep solar aspects this interface presents as a crust, there may be locations where the surface hoar actually sits on the crust. Potential exists for this layer to become increasingly reactive as new snow adds load to the snowpack. Slab releases or loose snow avalanches formed of new snow may also act as a trigger for this layer.The middle and lower portions of the snowpack are generally well-settled and strong.

Problems

Storm Slabs

An icon showing Storm Slabs
Incoming storm snow is unlikely to bond well to the old surface which is a mix of sastrugi, stubborn old wind slabs, facets, crust and surface hoar. Watch for fast moving sluff and touchy slabs forming as storm snow stacks up on Friday.
Conditions are expected to deteriorate throughout the day.Watch your sluff: it may run faster and further than you expect.If triggered, storm slabs may step down to deeper layers and result in even larger avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
15 to 45 cm of snow sits above a weak interface of surface hoar and crust. The recent warm to cold temperature transition has allowed a more cohesive slab to form above the surface hoar which is most prevalent at and below treeline.
Surface hoar distribution is highly variable. Avoid generalizing your observations.Avoid convex rolls at and below treeline where buried surface hoar may be preserved.Use extra caution around steep open terrain features, such as cutblocks, gullies and cutbanks.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Feb 1st, 2019 2:00PM

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