Avalanche Forecast

Issued: Jan 30th, 2018 4:07PM

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

shorton, Avalanche Canada

Northwest Coastal.

Large destructive avalanches are very likely as new snow accumulates. Stick to simple low-angled terrain.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

WEDNESDAY: Snow with accumulations of 5-10 cm Tuesday night and 5-10 cm on Wednesday / moderate southwest wind / alpine temperatures around -5 C.THURSDAY: Flurries, accumulations of 5-10 cm / moderate southwest wind / alpine temperatures around -7 C.FRIDAY: Snow with accumulations of 15-30 cm / moderate to strong southwest wind / alpine temperatures around -7 C.

Avalanche Summary

Natural avalanche activity was likely widespread during Tuesday's storm.Reports from Monday include a cycle of natural storm slab avalanches (up to size 2), several small (size 1) human-triggered slab avalanches, and dry loose avalanches (up to size 1.5). On Saturday, a size 2 remotely (from a distance) triggered persistent slab avalanche was reported to have run on a northeast aspect in the alpine on buried layer of surface hoar.

Snowpack Summary

Heavy snowfall in the Terrace area has delivered over 50 cm of new snow at the time of publishing (4 pm Tuesday), with another 10-20 cm possible by Wednesday afternoon. With this much new snow, storm slabs will be very touchy.60-100 cm of snow now covers a widespread layer that was buried in mid-January. This layer is primarily a crust, while surface hoar may be found in sheltered areas at treeline and below. Last week this weak layer produced sudden results in the Shames area and avalanche activity at upper treeline and alpine elevations. Professionals have also been monitoring a few deeper layers including a 100-140 cm deep crust / surface hoar layer that was buried in early-January, and a similar layer buried in mid-December that now lies 120-150 cm below the surface. Both of these layers have been reactive in recent snowpack tests and produced large natural avalanches in northern parts of the region near Bear Pass.The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.

Problems

Storm Slabs

Over 50 cm of new snow has formed very touchy storm slabs, especially in wind-affected terrain at higher elevations.

Minimize exposure during periods of heavy loading from new snow and wind.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Persistent Slabs

Buried weak layers in the snowpack have produced some recent large avalanches in steep, unsupported terrain. These layers may be sensitive under the weight of all the new snow.

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.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

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