Avalanche Forecast

Sea To Sky

Date issued

Jan 18, 2018 - 4:54 PM

Valid until

Jan 19, 2018 - 2:00 PM

Prepared by

jmcbride

New snow and wind have formed touchy storm slabs particulary at upper elevations.  With more snow in the forecast, choose moderate, low consequence terrain and carefully monitor how the new snow is bonding.

Regular season
Thursday - January 18, 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.

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

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.

Avalanche Problem 1: Storm Slabs

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

New snow combined with strong southerly winds has formed touchy 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
  • Be cautious as you transition into wind affected terrain.
  • Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Avalanche Summary

Ski cuts and explosive control work on Thursday produced numerous size 1-1.5, up to size 2, storm slab avalanches, 20-50 cm deep, 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.

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, 25-50 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.

At lower elevation below treeline the new storm snow is wet and heavy with moist snow below.

Weather Forecast

TONIGHT: Snow. Accumulation 10-15 cm. Ridge wind moderate, southwest. Temperature -6. Freezing level 1000 m.

FRIDAY: Cloudy, snow. Accumulation 10-15 cm. Ridge wind moderate, southwest. Temperature -3. Freezing level 1100 m.

SATURDAY: Cloudy, snow. Accumulation 10-20 cm. Ridge wind moderate, south. Temperature -4. Freezing level 1000 m.

SUNDAY: Cloudy, snow. Accumulation 10-20 cm. Ridge wind moderate south. Temperature -6. 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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