Avalanche Forecast

Issued: Jan 12th, 2019 3:53PM

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.

mconlan, Avalanche Canada

North Columbia.

Warm air and sunny skies have arrived at higher elevations. The amount of warming and its influence on the snowpack is uncertain. Travel conservatively and observe for signs of snowpack warming -- conditions may change rapidly over the day.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

SATURDAY NIGHT: Partly cloudy skies, inversion conditions with above-freezing layer between 1700 m and 2500 m.SUNDAY: Clear skies, light southwest winds, alpine temperature -1 to 1 C, inversion conditions with above-freezing layer between 1700 m and 2400 m.MONDAY: Clear skies, light west winds, alpine temperature -1 to 3 C, inversion conditions with above-freezing layer between 1700 m and 2500 m.TUESDAY: Clear skies, light southwest winds, alpine temperature -1 C, freezing level dropping to below valley bottom.

Avalanche Summary

A few storm slab avalanches were triggered naturally, by skiers, and by explosives on Friday. They were small to very large (size 1 to 3.5), on all aspects, and generally at treeline and alpine elevations. See here for a recent report.For the weekend, the likelihood of triggering storm slabs may increase due to the substantial amount of warming expected around upper below treeline, treeline, and alpine elevations. Also watch out in thin snowpack areas, where the likelihood of triggering deeper layers is the highest. See here for a recent example.

Snowpack Summary

Warm upper-level air temperatures and sunny skies may be impacting the snow surface. You may find dry snow, moist snow, or possibly a frozen melt-freeze crust, depending on how warm the air temperatures are. The warm air may produce touchy storm slabs at all elevations and particularly touchy on south aspects if the sun is strong. At the highest of elevations, wind slabs may still linger in lee and cross-loaded terrain features.The middle and lower portions of the snowpack are generally well-settled and strong. However, there still remain a few deeper weaknesses in the snowpack around treeline and alpine elevations. Professionals are still tracking a layer around 150 to 200 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack may also still be composed of weak faceted grains. These layers would most likely be triggered by humans in areas where the snowpack is shallow. The likelihood of triggering these layers may increase with the warm air expected to last until Tuesday.

Problems

Storm Slabs

There is uncertainty in how much the warm air and sunny skies will affect the snowpack, but it could make slabs reactive to human traffic. Observe for signs of warming, like moist snow, pinwheeling, or sluffing. Back-off if you notice instability.

Avoid steep slopes on warm and sunny days.Cornices may be touchy; stay well-back on ridges and avoid traveling beneath them.Look for signs of instability such as whumpfs, hollow sounds, shooting cracks, or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

There have been a few recent large avalanches on deeper layers within the region. The likelihood of triggering a deeper layer may increase with the warm weather.

Warm weather will increase the chance of triggering a deeper layer.Be aware of thin areas, where a triggered weak layer may propagate to deeper snowpack areas.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2.5 - 3.5

Valid until: Jan 13th, 2019 2:00PM