Avalanche Forecast

Issued: Nov 25th, 2017 4:32PM

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

cgarritty, Avalanche Canada

Northwest Inland.

Reports from the region have been limited and it is essential to supplement this forecast with your own observations as well as conservative travel techniques. Please post your observations to the Mountain Information Network. (MIN)

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Sunday: Cloudy with flurries bringing approximately 7 cm of new snow. Moderate southeast winds. Alpine temperatures of -5.Monday: Mainly cloudy with isolated flurries and a trace of new snow, increasing in the evening. Strong southwest winds. Alpine temperatures around -6.Tuesday: Mainly cloudy with scattered flurries bringing approximately 5 cm of new snow. Moderate to strong southwest winds. Freezing level rising to 1300 metres with alpine temperatures around -3.

Avalanche Summary

One report from Wednesday discussed several estimated Size 2.5-3 avalanches observed on the Kathlyn face of Hudson Bay Mountain. A recent report from social media showed a Size 2 avalanche that occurred last Monday in alpine terrain in the Babines. In spite of its age, the slide is notable for apparently having run on the late October persistent weak layer. No other new avalanches have been reported. Please post your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Snowpack depths over the south of the region are above average for late November, with approximately 150 cm of settled snow present at treeline elevations and above. Stormy weather last week delivered about 40 cm of new snow to the region and there is a good likelihood of wind slabs remaining reactive in open terrain where wind effects were more pronounced during and since the storm. Mid-treeline and lower elevations did receive some precipitation as rain toward the end of the storm, but the thin crust that resulted is not expected to offer bridging strength to the snowpack. About 20-30 cm of settled storm snow lies below last week's accumulations and above the widespread late October crust. This October crust is present near the base of the snowpack at all elevations and features a layer of weak, sugary grains above it. This "crust/facet combo" layer remains an ongoing concern for step-down potential from large triggers such as a storm slab release. The crust is less of a concern below treeline where it is broken up by vegetation near the ground.

Problems

Storm Slabs

Even as storm slabs gradually heal to the surface, south to southeast winds and light new snow inputs are incrementally loading the snowpack. Watch for this problem to become gradually limited to lee features in wind affected terrain.

Use caution in lee areas at treeline and above. New snow and winds continue to build touchy slabs.Avoid steep convexities and areas with variable snow distribution.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

The late October crust lies near the base of the snowpack and a layer of weak, sugary snow sits above it. This layer may react to a heavy trigger like a wind slab release. The first evidence of avalanche activity on this layer was recently reported.

If triggered, storm slabs may step down to deeper layers and result in large avalanches.Be aware of the potential for large avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Nov 26th, 2017 2:00PM