Avalanche Forecast

Issued: Feb 3rd, 2018 5:15PM

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

shorton, Avalanche Canada

Northwest Inland.

Stormy weather could eventually tip the scales and initiate a natural avalanche cycle that may involve buried weak layers. Conservative terrain selection and avoiding overhead hazards is recommended.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

SUNDAY: The Arctic front delivers another 10-15 cm of snow with moderate southeast wind, potential for an inversion with alpine high temperatures around -8 C.MONDAY: A break from the storm with isolated flurries, moderate west wind, alpine high temperatures around -6 C.TUESDAY: Another storm brings 15-25 cm with strong to extreme southwest wind and freezing levels climb to roughly 1500 m.

Avalanche Summary

Reports have been limited. At the start of the storm on Wednesday and Thursday skiers triggered a few small slabs on steep convex rolls.There are no recent reports of persistent slab avalanche activity, but some notable large avalanches occurred 5-8 days ago. This includes some large (size 2-3) natural persistent slab avalanches in the Howsons, and two large (size 2.5) remotely triggered avalanches north of Kispiox. We have no information from the Smithers area, but suspect a similar deeper weakness could exist there too. Activity on buried weak layers is most suspect during periods of heavy loading or rapid warming, hence it's time to be cautious.

Snowpack Summary

Fresh snow will continue to accumulate the next few days. 30-50 cm has already accumulated since Thursday. The snow has mostly fallen as low density powder, but may have settled in some areas that experience a brief period of warming on Friday. Westerly winds are likely blowing snow around in exposed terrain and forming touchy slabs.40-70 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. Another two crust / surface hoar layers that formed in December are buried 60-90 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Problems

Storm Slabs

New snow and wind will form touchy slabs, especially at higher elevations and in wind-affected terrain.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Minimize exposure during periods of heavy loading from new snow and wind.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

There is limited information about weak layers buried 30-80 cm below the surface. They produced a few large avalanches last week, and may become more reactive with ongoing loading.

Avoid lingering in runout zones.Evaluate unsupported slopes critically.Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 2.5

Valid until: Feb 4th, 2018 2:00PM