Avalanche Forecast

Sea To Sky

Date issued

Jan 16, 2018 - 4:51 PM

Valid until

Jan 17, 2018 - 2:00 PM

Prepared by

jmcbride

New snow and wind have created touchy storm slabs above the crust that formed with recent warm temperatures.  These slabs will continue to build and hazard rise as the next storm system arrives on Wednesday.

Regular season
Wednesday - January 17, 2018
Alpine

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.

Treeline

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.

Below 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.

Thursday - January 18, 2018
Alpine

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.

Treeline

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.

Below Treeline

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.

Friday - January 19, 2018
Alpine

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.

Treeline

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.

Below Treeline

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.

Avalanche Problem 1: Storm Slabs

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

Loading from new snow and strong winds will create widespread storm slabs. A release near the surface may still have the potential to step down to a deeper layer.

Travel and Terrain Advice
  • Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Avalanche Summary

Tuesday, explosive control work and ski cutting produced numerous size 1-1.5 storm slab releases on leeward aspects at treeline and into the alpine, running on the January 15th crust.  Expect this activity to increase as more snow and strong winds forecasted for Wednesday and Thursday.

Warm alpine temperatures on Sunday produced numerous naturally triggered loose wet and wet slab avalanches mostly in the size 1-1.5 range, and a few up to size 2 on solar aspects.

Snowpack Summary

Above 1600 m elevation, 20-40 cm of new snow overlies the January 15th crust which exists on all aspects and elevations. This crust is thin on northerly aspects and up to 3 cm thick on solar aspects. Below this crust 30-40 cm of moist, well settled snow overlies the January 6th crust which is now buried 40-80 cm below the surface and exists up to about 2000m.

Beneath the January 6 crust, the lower snowpack is generally strong and well settled.

Weather Forecast

TUESDAY NIGHT: Flurries. Accumulation 2-5 cm. Ridge wind moderate, south. Temperature -2. Freezing level 1000 m.

WEDNESDAY: Cloudy, snow. Accumulation 30-40 cm. Ridge wind strong to extreme, south. Temperature near 0. Freezing level rising to 1600 m.

THURSDAY: Cloudy, snow. Accumulation 15-25 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1000 m.

FRIDAY: Cloudy, snow. Accumulation 5-15 cm. Ridge wind moderate, south. Temperature -3. Freezing level 900 m.

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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