Avalanche Forecast

Issued: Jan 30th, 2018 4:27PM

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.

shorton, Avalanche Canada

Northwest Inland.

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

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

WEDNESDAY: Isolated flurries with accumulations of 5-10 cm / light to moderate southwest wind / alpine temperatures around -8 C.THURSDAY: Isolated flurries / light to moderate south wind / alpine temperatures around -10 C.FRIDAY: Flurries with accumulations of 10-15 cm / moderate southwest wind / alpine temperatures around -12 C.

Avalanche Summary

Most of the recent reported activity has been loose dry surface snow sluffing in steep terrain. On Monday, a large size 3 slab avalanches was reported on an east aspect at 1900 m in the Howsons.On Friday, a helicopter remotely triggered a size 2.5 wind slab from above the slope on a west aspect at 1500 m north of Kispiox. On Thursday, skiers north of Kispiox remotely triggering a size 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

Strong winds have built wind slabs in exposed terrain. 30-60 cm 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 treeline elevations. Below, there are two crust and/or surface hoar layers that were buried in 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 lee aspects in the alpine and wind-exposed areas at treeline. They overlie a thin crust / surface hoar layer and have been reactive to light triggers.

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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Valid until: Jan 31st, 2018 2:00PM