Avalanche Forecast

Issued: Feb 14th, 2018 4:45PM

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

jmcbride, Avalanche Canada

Lizard-Flathead.

Storm slabs, cornices and deeply buried weak layers are making for tricky conditions. The best approach is to choose conservative terrain, minimize your exposure to overhead hazards and avoid freshly wind-loaded areas.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

TONIGHT: Cloudy, flurries. Accumulation 2-6 cm. Ridge wind moderate northeast. Temperature -15. Freezing level valley bottom.THURSDAY: Mix of sun and cloud. Ridge wind strong west. Temperature -10. Freezing level valley bottom.FRIDAY: Mix of sun and cloud, light flurries. Accumulation up to 5 cm. Ridge wind moderate, west. Temperature -10. Freezing level valley bottom.SATURDAY: Snow. Accumulation 15-20 cm. Ridge wind moderate to strong, east. Temperature -15. Freezing level valley bottom.

Avalanche Summary

Explosive control work on Wednesday produced widespread storm slab results up to size 2, between 1600-2100 m.On Tuesday skiers were able to cut size 1.5 wind slabs on north east features at treeline. Wind slabs to size 2 were also reported, starting at the base of steep head walls. On Saturday we received reports of impressive sizes of cornice chunks breaking off a tree line ridge feature near Harvey Pass (Flathead area), running far into the forest and meadow below. See here for photos. On Saturday, explosive control produced wind slab results up to size 2 on north facing slopes near 2000m. Avalanche activity on deeper layers has tapered off for now, but it's best to avoid likely trigger points such as thick-to-thin snow pack areas and also close to the base of rocky headwalls.

Snowpack Summary

About 20 cm of new storm snow overlies old wind slabs leeward slopes at treeline and above. Below 1700m, this new snow covers a rain crust from last Wednesday. For the past month there has been regular avalanche activity on multiple weak layers in the mid and lower snowpack. A widespread weak layer from mid December composed of facets, crusts, and surface hoar is 120-160 cm deep. Also, a rain crust with sugary facets buried in late November is near the base of the snowpack.The take home message is that several weak layers are still lurking in the snowpack and they deserve a lot of respect. Conservative terrain use is recommended while avoiding all overhead hazard.

Problems

Storm Slabs

New snow and wind have formed storm slabs particularly in wind exposed areas above 1600 m for the Fernie area. This new snow overlie areas of wind-affected and scoured snow and is not bonding well to the old surface.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Large avalanches have been running on deep weak layers. Wind loading, fragile cornices, and smaller avalanches are all possible triggers, as well as thin or rocky snowpack areas where human triggering may also be possible.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Be aware of the potential for large, deep avalanches.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Cornices

Cornices have triggered very large avalanches recently. Be especially wary of long runout distances in avalanche paths, and the possibility of mature timber being taken out by a surprisingly large avalanche.

Give cornices a wide berth when traveling on or below ridges.Avoid steep slopes below cornices.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3.5

Valid until: Feb 15th, 2018 2:00PM