Avalanche Forecast

Sea To Sky

Date issued

Jan 19, 2018 - 4:36 PM

Valid until

Jan 20, 2018 - 2:00 PM

Prepared by

jmcbride

Recent snow and wind have formed storm slabs that will continue to build with more snow and wind forecasted for the weekend. Carefully monitor how the new snow is bonding and watch for freshly wind-loaded areas.

Regular season
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

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.

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

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.

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.

Avalanche Problem 1: Storm Slabs

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

Recent storm snow and strong southerly winds has formed cohesive storm slabs particularly at upper treeline and alpine elevations. These slabs overlie a recent melt-freeze crust and will continue to build with more snow and wind in the forecast.

Travel and Terrain Advice
  • Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.
  • Be cautious as you transition into wind affected terrain.
  • Minimize exposure during periods of heavy loading from new snow and wind.

Avalanche Summary

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.

Wednesday ski cutting and explosive control work produced numerous easily triggered size 1 storm slab results up to 40 cm deep running on the January 15th crust. And on 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.

Snowpack Summary

Above 1400 m elevation, 50-70 cm of storm snow overlies the January 15th crust which 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 of moist, well settled snow overlies the January 6th crust which is now buried about 100 cm below the surface and exists up to about 2000m. Beneath the January 6th crust, the lower snowpack is generally strong and well settled.

Weather Forecast

Upper range snowfall amounts are expected for areas in the southern part of the region.

TONIGHT: Snow. Accumulation 5-10 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 800 m.

SATURDAY: Snow. Accumulation 15-30 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 900 m.

SUNDAY: Snow. Accumulation 20-40 cm. Ridge wind strong, southwest. Temperature -4. Freezing level 900 m.

MONDAY: Flurries. Accumulation 5-15 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 800 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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