Avalanche Forecast

South Coast Inland

Date issued

Feb 11, 2018 - 5:00 PM

Valid until

Feb 12, 2018 - 2:00 PM

Prepared by

mgrist

Winds have formed pockets of reactive wind slab on leeward and cross-loaded slopes at upper elevations. Also keep an eye on what's above or below you. Cornices are large and may become fragile with warm temperatures or sun-exposure.

Regular season
Sunday - February 11, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Monday - February 12, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Tuesday - February 13, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Below Treeline

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

Avalanche Problem 1: Wind Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Reactive wind slabs exist, especially on leeward slopes where more wind loading has occurred.

Travel and Terrain Advice
  • Be cautious as you transition into wind affected terrain.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Avalanche Problem 2: Cornices

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Recent snowfall and strong winds have created large fragile cornices. Cornices are unpredictable and demand respect. Give them a wide berth from above and below, especially during periods of warming or sun-exposure.

Travel and Terrain Advice
  • Give cornices a wide berth when traveling on or below ridges
  • Falling cornices may trigger large avalanches on slopes below.

Avalanche Summary

On Saturday, skiers triggered a size 2 wind slab on a north east aspect near 2000m in the Duffey zone. See the MIN report for more details.

Friday there were isolated reports of natural cornice triggered and wind slab activity up to size 2.5, as well as evidence of an older large, natural size 3.5, in high alpine terrain in the Duffey Lake area.

On Thursday, the southern part of the region reported a natural slab avalanche size 3.5 from a NE-SE aspect near 1800 m and numerous wet slabs up to size 2.5. An avalanche control mission using explosives in the northern part of the region saw wind slab results up to size 1.5, only running in the surface snow and not stepping down deeper.

Snowpack Summary

Last week's snowfall totals are highly variable. In the south, up to 40 cm of new snow fell bringing the alpine totals up to 60 cm for the storm ending last week. In the north, new snow totals are half that and rapidly decrease below 1800m. This new snow remains unconsolidated in wind-sheltered, shaded areas at upper elevations but has formed wind slabs in open areas at treeline and above, and scoured areas at ridge crests.

At lower elevations travel is rugged and some are recommending ski crampons below tree line (!)

Below the snow surface, 80-150 cm down in the mid pack sits the mid- January crust. It generally shows signs of bonding to the overlying snow; however, I would remain suspect of this deeper layer while the snowpack adjusts to the new load. Thinner snowpack areas may have a higher likelihood of an avalanche failing on this layer. Large, looming cornices exist, they are fragile and demand respect.

Weather Forecast

MONDAY: Mostly sunny. Ridge wind moderate, northwest. Temperature -5. Freezing level 500 m. Alpine inversion.

TUESDAY: Mostly cloudy, light flurries. Accumulation up to 5 cm. Ridge wind moderate gusting strong from the west. Temperature -5. Freezing level 500 m.

WEDNESDAY: Cloudy with some lingering flurries. Ridge wind moderate, northwest. Temperature -5. Freezing level 700m.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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