Avalanche Forecast

Issued: Feb 12th, 2018 4:21PM

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

mgrist, Avalanche Canada

Lizard-Flathead.

Wind slabs are the main concern at higher elevations - they may sit on several critical weak layers. Give cornices a wide berth too, and be aware of overhead hazard as you travel.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at cool temperatures and some gusty west through north winds for the next few days. Overnight lows will be near -20 Celsius at tree line. TUESDAY: A mix of sun and cloud. Ridge wind becoming strong from the west. Temperature -7. Freezing level 1100m in the afternoon.WEDNESDAY: Flurries (5 -15cm accumulation). Ridge wind moderate gusting strong from the north / east. Temperature -7. Freezing level valley bottom.THURSDAY: Sunny with cloudy periods. Ridge wind gusting moderate from the west. Temperature -10. Freezing level valley bottom.

Avalanche Summary

On Saturday, explosive control produced wind slab results up to size 2 on north facing slopes near 2000m. A week ago, a snow cat remotely (from a distance) triggered a size 3-3.5 persistent slab avalanche that stepped down from 80-250 cm and ran to ground in the lower start zone on a south aspect at 2100 m. Also a week ago, the east facing Mt. Corrigan slidepath produced a very large, natural avalanche. The avalanche is estimated to be a size 4.0, and it took out mature timber in the path as it overran the Flathead FSR south of Corbin.

Snowpack Summary

New snow totals from last week vary from 5-20cm above 1700m, thanks to redistribution from variable winds. Wind slabs up to 20cm thick have formed on down wind (lee) features higher up. Below 1700m, rain last Wednesday formed a thick crust and capped the snow pack. That said, avalanche hazard remains elevated below tree line due to the possibility of large avalanches running full path from higher elevations. 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 deserve a lot of respect. Conservative terrain use is recommended while avoiding all overhead hazard.

Problems

Wind Slabs

New snow and strong wind have formed reactive wind slabs particularly in wind exposed areas above 1700 m for the Fernie area.

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

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.Extra caution needed around cornices with current conditions.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Feb 13th, 2018 2:00PM