Avalanche Forecast

Sea To Sky

Date issued

Feb 21, 2018 - 4:06 PM

Valid until

Feb 22, 2018 - 2:00 PM

Prepared by

swerner

Natural avalanche activity has tapered but wind slabs continue to be reactive to human triggering. Pay attention to overhead hazards like cornices, especially when the sun is out.

Regular season
Wednesday - February 21, 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.

Thursday - February 22, 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.

Friday - February 23, 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?

Strong winds from various directions (primarily north and east) have blown recent snow into stiff wind slabs at treeline and above.

Travel and Terrain Advice
  • Sheltered slopes at lower elevations will offer the best riding.
  • Approach steep lee and cross-loaded slopes with caution.
  • Use ridges or ribs to avoid pockets of wind loaded snow.

Avalanche Problem 2: Cornices

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

Large cornices have formed along ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.

Travel and Terrain Advice
  • Minimize overhead exposure to cornices above, they could trigger a slab from the slope below.
  • Give cornices a wide berth when traveling on or below ridges.

Avalanche Summary

With the benign weather pattern natural avalanche activity has tapered. However, human triggered wind slabs are possible at upper elevations on most aspects but the north.

Snowpack Summary

Highly variable surface conditions exist with extensive wind effect. In exposed terrain, strong north winds have scoured north facing slopes and loaded south facing slopes. In sheltered terrain, especially in the trees you may be able to find 30-40 cm of low density snow. A crust layer can be found beneath the storm snow on sun-exposed slopes and below 1900 m, which has supported some wide propagations in recent storm slab avalanches.

Deeper in the snowpack, avalanche professionals are still monitoring the mid-January crust. This layer is now 150-200 cm deep, but a heavy trigger (cornice?) or the next major storm (warming and loading) could potentially wake up this layer.

Weather Forecast

Thursday: Mostly sunny with alpine temperatures near -11. Ridgetop winds light from the North.

Friday: Overcast with new snow amounts 5-10 cm. Alpine temperatures near -9 and ridgetop winds strong from the southwest.

Saturday: Mix of sun and cloud. Alpine temperatures near -9. Light to moderate winds from the northwest.

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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