Avalanche Forecast

Issued: Jan 29th, 2018 4:37PM

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

mbender, Avalanche Canada

Northwest Inland.

New snow and wind will continue to build wind slabs in the alpine and tree line elevations. Triggering persistent slabs from thin snowpack areas remains a concern in the north of the region.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

TUESDAY: Isolated flurries, accumulations 5-10cm Monday night into Tuesday / Moderate to strong southwest wind / Alpine temperature -5 WEDNESDAY: Isolated flurries / Light to moderate southwest wind / Alpine temperature -7 THURSDAY: Isolated flurries / Light to moderate south wind / Alpine temperature -6

Avalanche Summary

Most recent avalanche activity has been reported as loose dry surface snow sluffing to size 1 in steep terrain. Friday there was a report of a helicopter remotely triggering a Size 2.5 wind slab from above the slope on a west aspect at 1500 m north of Kispiox. Thursday there was a report of skiers, north of Kispiox, remotely triggering a Size 2-2.5 avalanche from a safe location on a ridge that released on the adjacent slope on a northwest aspect at 1650 m. A weak layer buried late-December was the suspected failure plane.

Snowpack Summary

30-70cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and tree line elevations. Below, there are two separate crust and/or surface hoar layers that were buried late-December and mid-December. They are 50-80 cm below the surface. In the past week these deeper layers have produced hard but sudden results in snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Problems

Wind Slabs

Wind slabs can be found on leeward aspects in the alpine as well as wind-exposed areas at treeline. These slabs overlie a thin crust/ surface hoar layer and have been reactive to light triggers especially in steep or convex terrain near ridge crests.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Weak layers buried in the snowpack have produced recent avalanches particularly on unsupported features.

Watch for signs of instability such as whumpfing, or cracking at lower elevations.Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Jan 30th, 2018 2:00PM