Avalanche Forecast

Issued: Feb 13th, 2018 5:07PM

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

mgrist, Avalanche Canada

Lizard-Flathead.

Wind slabs, cornices and persistent slabs make for a tricky situation out there. Ride in conservative terrain and avoid all overhead hazard to manage your risk.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

Wednesday will see an upslope event bringing small amounts of low density snow, followed by clearing and unsettled weather. TUESDAY NIGHT: Flurries (5-10cm of low density snow). Winds moderate gusting strong from the north west. WEDNESDAY: Flurries (5 -10cm accumulation). Ridge wind moderate gusting strong from the north / west. Temperature -7. Freezing level valley bottom.THURSDAY: Sunny with cloudy periods. Ridge wind gusting moderate from the west. Temperature -9. Freezing level valley bottom.FRIDAY: Isolated flurries. Ridge wind becoming strong from the southwest. Temperature -5. Freezing level 1000m in the afternoon.

Avalanche Summary

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

Since the last snowfall almost a week ago, we've seen gusty winds (strong at times) from virtually all directions. The end result is wind slabs up to 20cm thick have formed on down wind (lee) features higher up, on a wide range of aspects. Below 1700m, rain last Wednesday formed a thick crust and capped the snow pack. 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

Wind Slabs

Strong winds formed reactive wind slabs particularly in wind exposed areas above 1700 m for the Fernie area.

If triggered, the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - 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.

Extra caution needed around cornices with current conditions.Be aware of the potential for large, deep avalanches.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3.5

Valid until: Feb 14th, 2018 2:00PM