Avalanche Forecast

South Coast Inland

Date issued

Jan 18, 2018 - 4:45 PM

Valid until

Jan 19, 2018 - 2:00 PM

Prepared by

jmcbride

Snow and wind are expected to continue however, there is some uncertainty as to just how much snowfall some areas will see.  If trail breaking is deep and heavy, storm slabs have likely formed - stick to moderate terrain.

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 and strong winds will build touchy storm slabs particulary on lee slopes at upper treeline and alpine elevations. In northern parts of the region it may still be possible for a surface release to step down to a deeper layer.

Travel and Terrain Advice
  • Minimize exposure during periods of heavy loading from new snow and wind or rain.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Avalanche Summary

On Wednesday several natural and skier triggered avalanches from size 1 to 1.5 where reported at treeline and alpine elevations. Most of these were failing on the recent January 15th crust however one ski cut result was believe to have failed on the January 6th crust at 1950 m on a north aspect.

Reports from Tuesday indicate that the new snow had formed thin wind slabs that were reactive to skier triggers but had little mass or consequence. Expect this to change as new snow amounts accumulate with the approaching storm.

On Sunday there was a report of a skier triggered size 2.5 slab avalanche in the northern part of the region that initiated as a 30 cm thick wind slab then stepped down to approximately 70 cm thick (likely the mid December layer) on a north-east aspect at 2050 m.

Snowpack Summary

Approximately 40-50 cm of new storm snow has buried the most recent, January 15th crust. This crust exists on almost all aspects and elevations with the exception of northerly aspects above 1850 m where the snow surface remained dry during the alpine inversion event on the weekend.

Below the January 15th crust about 30-50 cm of snow overlies a 1 cm thick crust that was buried on January 6th which exists up to about 2000m.

Mid and lower snowpack layers including the mid December and late November crust layers have produced moderate to hard, sudden results in snowpack tests in the northern part of the region last week and may be a concern for step-down potential.

Weather Forecast

Southern parts of the region can expect to see higher snowfall amounts than northern areas.

TONIGHT: Flurries. Accumulation 1-5 cm. Ridge wind moderate, southwest. Temperature -7. Freezing level 800 m.

FRIDAY: Cloudy, snow. Accumulation 5-15 cm. Ridge wind moderate, southwest. Temperature -3. Freezing level 1200 m.

SATURDAY: Cloudy, snow. Accumulation 2-10 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 1000 m.

SUNDAY: Cloudy, snow. Accumulation 5-15 cm. Ridge wind moderate to strong, south. 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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