Avalanche Forecast

Issued: Nov 30th, 2017 4:39PM

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

swerner, Avalanche Canada

Northwest Inland.

The late October crust near the base of the snowpack is reactive to rider triggers producing large avalanches. You could trigger this from a significant distance away. Heads up out there as this problem will likely persist.

Summary

Confidence

Low - Due to the number and quality of field observations

Weather Forecast

Friday: Cloudy with possible flurries. Strong ridgetop winds from the West. Alpine temperature -10. Freezing level 500 m and dropping.Saturday: Mix of sun and cloud. Light ridgetop winds from the North West. Alpine temperature -15. Freezing level valley bottom.Sunday: Mostly sunny with some residual cloud. Strong ridgetop winds from the North West. Alpine temperature -12. Freezing level valley bottom. Visit the Mountain Weather Forecast for more details.

Avalanche Summary

On Tuesday, skiers up Skilokis Creek area reported remotely triggering a large (Size 2.5) avalanche from 150 m away as they approached a north-facing, treeline bowl. The avalanche was triggered from a shallow snowpack area and failed on a weak facet layer just above the late October crust near the base of the snowpack. The persistent slab was 80 cm deep, 120 m wide and ran 300 m in length. The week before that, several estimated Size 2.5-3 avalanches were observed on the Kathlyn face of Hudson Bay Mountain and are also suspected to have failed on the late October crust. This "crust/facet combo" layer is capable of producing very large avalanche and is expected to remain a layer of concern for some time. Please post your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Average Snowpack depths are 100-140 cm at treeline elevations, and up to 160 cm in the alpine. Approximately 30-40 cm of recent snow now overlies the supportive November 23 crust. This crust extends well into alpine elevations. Below this crust is a well settled mid pack that sits on the widespread late October crust near the base of the snowpack at all elevations. This late October "crust/facet combo" layer has been very reactive to rider triggers producing large avalanches.

Problems

Deep Persistent Slabs

The late October crust lies near the base of the snowpack with a thin layer of weak, sugary snow above it. This layer has been reactive to rider triggers and remote triggering has occurred.

Be aware of the potential for large avalanches due to weak layers at the base of the snowpack.Be cautious in shallow snowpack areas where triggering a deeper layer may be possible.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Wind Slabs

Recent snow and wind have formed touchy wind slabs. Expect these slabs to be more pronounced at higher elevations and on leeward aspects. Watch for signs of wind affected snow, whumpfing and cracking.

Avoid steep convexities and areas with variable snow distribution.Watch for signs of instability such as whumpfing, hollow drum-like sounds or shooting cracks.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 1st, 2017 2:00PM