Avalanche Forecast

Issued: Jan 18th, 2017 4:15PM

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

triley, Avalanche Canada

Northwest Inland.

The storm continues to develop storm slabs above a weak shallow snowpack. Storm slab avalanches in motion may step down and result in large avalanches.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Freezing levels dropping to near valley bottoms overnight combined with moderate southwest winds and 3-5 cm of new snow. Overcast with flurries or light snow on Thursday and moderate southwest winds. Freezing near valley bottoms and -5 in the alpine. Clearing and cooler on Friday with light winds and alpine temperatures near -10. Overcast with moderate southeast winds and a chance of flurries on Saturday.

Avalanche Summary

Expect developing storm slabs to be easy to trigger where they are sitting on a weak layer of surface hoar and/or a crust left behind after the cold and windy weather. Full depth avalanches continue to be a concern due to the weak facetted snowpack below the hard wind slabs left behind after strong winds from several directions. This deep persistent weak layer may take prolonged warm weather with consistent snowfall to settle and bond.

Snowpack Summary

20-25 cm of new storm snow that has been transported by the southwest winds now sits on a mix of old surfaces left behind after the recent cold and windy weather. Expect the new storm snow to bond poorly where it is sitting on a weak layer of buried surface hoar and/or a hard old wind polished surface. Most areas continue to have a shallow and weak snowpack that is about 120-150 cm at treeline. In general, the snowpack above treeline has been heavily wind effected; this has resulted in hard wind slabs above weak facettted crystals. The snowpack below treeline in sheltered areas may be unconsolidated with foot penetration close to the ground.

Problems

Deep Persistent Slabs

Storm snow combined with warming and wind has added a load above the hard slabs that are sitting on a weak facetted base. Uncertainty revolves around what type of load is now required to trigger these deep persistent slabs.

Avoid slopes with convexities or variable snowpack depths. Thin weak spots are likely trigger pointsStick to simple terrain and be aware of what is above you at all times.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

New snow, warm temperatures, and strong winds have created a widespread storm slab problem, particularly on wind-loaded features. Storm slab avalanches in motion may step down and trigger deep persistent slab avalanches.

The new snow will require several days to settle and stabilize.Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Loose Wet

The recent storm was rain below about 1000 metres. Rain on snow may result in loose wet avalanches in steep terrain below treeline.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 19th, 2017 2:00PM