Avalanche Forecast

Issued: Jan 19th, 2018 3:56PM

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 mbender, Avalanche Canada

The snowpack is complex. Three active weak layers remain sensitive to human triggering. The easy solution is to choose simple terrain free of overhead hazard as the snowpack adjusts.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

SATURDAY: Mix of sun, cloud and isolated flurries / Light to moderate southwest wind / Alpine temperature -10 / Freezing level 1100m SUNDAY: Flurries, accumulation 5-10cm / Moderate to strong south wind / Alpine temperature -10 / Freezing level 900m MONDAY: Scattered flurries / Light southwest wind / Alpine temperature -12 / Freezing level 800m

Avalanche Summary

On Thursday avalanche activity was reported as storm and persistent slabs. Storm slabs were running to size 2 on southerly and northerly aspects in the alpine and tree line. There were two persistent slab avalanches reported that were both skier triggered 80cm deep between 1100 and 1400m on north aspects. One of them was remotely triggered (from a distance) from 60m away and was a size 2.5. The other was triggered by a ski cut and was a size 1, yet still 80cm deep. On Wednesday a small natural avalanche cycle was reported from steep ridge features. Fast and loose sluffing was also reported.

Snowpack Summary

The current snowpack is complex, we now have three active weak layers that we are monitoring. 15-35cm of storm snow now sits on a newly formed crust and/or surface hoar interface. Prior to the storm the crust was reportedly widespread; high elevation north is likely one of the few crust-free zones. The now buried surface hoar is up to 10mm in size and was reportedly present at all elevations before the storm. Looking deeper, a persistent weak layer known as the early January interface is 30 to 60 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is present at all elevation bands. Recent snowpack tests have shown sudden results with moderate loads. Additionally, yet another persistent weak layer buried mid-December consisting of a facet/surface hoar/crust combination, is buried 40 to 100 cm deep. It is most problematic at and below tree line. This interface is not thought to be present in the alpine. A rain crust buried in November is 100 to 150 cm deep and is thought to have gone dormant for the time being.

Problems

Storm Slabs

An icon showing Storm Slabs
15 to 35cm sits on a combination of crust and surface hoar. Expect the slab to be deeper in wind exposed features and to be sensitive to human triggering.
Be very cautious as you transition into wind affected terrain, wind slabs may be deep and touchy.Carefully investigate the bond of the new snow before stepping out into more challenging terrain.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The riding conditions may be great, but we can't forget about the persistent weak layers lurking in our snowpack that remain quite capable of producing very large avalanches. Keep the terrain choices reined in as the snowpack adjusts to the new load.
Numerous large avalanches have run on these layers in well supported, treed terrain.Good day to make conservative terrain choices and watch for clues of instability.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Valid until: Jan 20th, 2018 2:00PM

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