Avalanche Forecast

Sea To Sky

Date issued

Jan 20, 2018 - 4:38 PM

Valid until

Jan 21, 2018 - 2:00 PM

Prepared by

jmcbride

With a strong winter storm system set to bring heavy snowfall and high winds, Sunday looks like a good day to enjoy the resort.  Or stick to simple terrain free of overhead hazard if you choose to venture into the backcountry.

Regular season
Saturday - January 20, 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

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.

Sunday - January 21, 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.

Monday - January 22, 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?

Storm snow and strong winds have formed reactive storm slabs. These slabs overlie recently buried wind slab and a recent melt-freeze crust, and will continue to build with more snow and wind in the forecast.

Travel and Terrain Advice
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • The new snow will take time to settle and stabilize.
  • Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.

Avalanche Summary

Both natural and human triggered avalanches are likely with intense loading from forecasted snowfall and wind amounts.

Explosive control work on Friday produced only a few size 1 and isolated size 2 avalanches failing in the recent storm snow or running on the recently buried January 15th crust.

On Thursday there were reports of natural avalanches up to size 2.5, while ski cuts and explosive control work produced numerous size 1-1.5, and up to size 2, storm slab avalanches 20-50 cm deep on predominantly northerly aspect, running far and wide within the recent storm snow.

Earlier in the week ski cutting and explosive control work produced numerous easily triggered size 1-1.5 storm slab results running on the January 15th crust.

Snowpack Summary

Above 1400 m elevation, 40-70 cm of storm snow overlies the crust that was buried mid-January and is present at all elevations. This crust is thin on northerly aspects and up to 3 cm thick on solar aspects. Below this crust 30-40 cm well settled snow overlies a second crust that was buried early-January and now lies about 100 cm below the surface at elevations up to 2000m. Beneath the early-January crust, the lower snowpack is generally strong and well settled.

Recent snowpack tests have produced easy to moderate, resistant results within the recent storm snow as well as hard, resistant results above the recently buried mid-January crust.

Weather Forecast

TONIGHT: Snow. Accumulation 30-40 cm. Ridge wind strong to extreme, south. Temperature -5. Freezing level 1000 m.

SUNDAY: Snow. Accumulation 25-35 cm. Ridge wind strong to extreme, south. Temperature -4. Freezing level 1000 m.

MONDAY: Flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southwest. Temperature -4. Freezing level 900 m.

TUESDAY: Snow. Accumulation 15-20 cm. Ridge wind strong, south. Temperature -4. 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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