Avalanche Forecast

Issued: Feb 4th, 2018 6:31PM

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.

ghelgeson, Avalanche Canada

Northwest Inland.

Storm slabs are expected to remain sensitive to human triggering and a window of sun Monday afternoon could initiate a round of natural avalanche activity. Take a cautious approach and minimize your exposure to overhead avalanche terrain.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

A strengthening ridge axis on Monday offers a brief lull in the action before the next system slams into the Northwest Coast on Tuesday before spilling into the Inland region on Wednesday.MONDAY: Broken cloud cover in the morning, clearing in the afternoon, freezing level at valley bottom, light to moderate west/northwest wind, trace of snow possible. TUESDAY: Overcast, freezing level at valley bottom, moderate to strong west/southwest wind, 1 to 5 cm of snow. WEDNESDAY: Overcast, freezing level at valley bottom, moderate west/southwest wind, 5 to 15 cm of snow.

Avalanche Summary

Reports have been limited. On Saturday a small storm slab was reportedly human triggered on an east facing aspect around 1000 m. 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

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 have likely formed touchy slabs, especially at higher elevations and in wind-affected terrain. There is potential for a brief window of strong sun Monday afternoon which could initiate a fresh round of storm slab avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid being on or under sun exposed slopes.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

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 remain sensitive to human triggering.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 2.5

Valid until: Feb 5th, 2018 2:00PM