Avalanche Forecast

Issued: Jan 19th, 2018 4:13PM

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 - Timing of incoming weather systems is uncertain

Weather Forecast

SATURDAY: Mix of sun, cloud and isolated flurries / Light to moderate southwest wind / Alpine temperature -8 / Freezing level 1200m SUNDAY: Flurries, accumulation 5-10cm / Light to moderate southwest wind / Alpine temperature -8 / Freezing level 1200m MONDAY: Scattered flurries / Light to moderate southwest wind / Alpine temperature -10 / Freezing level 800m

Avalanche Summary

Avalanche activity on Thursday included wind slab, storm slab and persistent slab activity. Storm slabs were reported mostly to size 1.5 on all aspects at tree line. One size 3 naturally triggered persistent slab avalanche was reported in the south of the region running on a northeast aspect in the alpine. Natural and explosives triggered wind slab avalanches were reported running to size 2 on east and north aspects in the alpine and tree line.

Snowpack Summary

The current snowpack is complex, we now have three active weak layers that we are monitoring. 10-30cm 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 10 to 30mm 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 40 to 80 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 110 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 90 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 30cm 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.
Carefully investigate the bond of the new snow before stepping out into more challenging terrain.Be very cautious as you transition into wind affected terrain, wind slabs may be deep and touchy.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

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.
Good day to make conservative terrain choices and watch for clues of instability.Numerous large avalanches have run on these layers in well supported, treed terrain.

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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