Date issued

Dec 2, 2017 - 6:12 PM

Valid until

Dec 3, 2017 - 4:00 PM

Prepared by

Tim Haggarty

Concern remains for the persistent slabs however natural activity has been limited to soft windslabs in the alpine. A new weather pattern will change the wind direction and affect future windslab development.

Regular season
Sunday - December 3, 2017
Alpine

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.

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.

Below Treeline

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.

Monday - December 4, 2017
Alpine

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.

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.

Below Treeline

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.

Tuesday - December 5, 2017
Alpine

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.

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.

Below Treeline

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.

Avalanche Problem 1: Persistent Slabs

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

Natural avalanche activity has tapered, but concern remains for human triggering of the weak snow on this layer. Previously, slab avalanches have been triggered above ~ 2400m where the Nov. 23rd crust fades out. Shallow alpine areas warrant caution.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • Avoid shallow snowpack areas where triggering is more likely.

Avalanche Problem 2: Wind Slabs

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

Up to 50cm of recent snow is available for transport TL and above. So far only light, gusting moderate, SW winds have created soft slabs and wind effect but watch for this to change as winds shift to the NW Sunday and then increase on Monday.

Travel and Terrain Advice
  • Use caution in lee areas. Recent wind loading has created wind slabs.
  • Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.

Avalanche Summary

A tour to the Ferris Glacier saw very little recent avalanche activity. One sz 2 natural windslab was seen out of a snowfield between two NE facing cliff bands at around 2700m. This freshly formed slab appeared to be 40 to 50 cm deep and likely was a result of wind driven sluffs spilling over the cliffs above.

Snowpack Summary

Below 2500m up to 50 cm of snow lies over the 1127 crust. Another crust (1123) can be found below this and both of these now overlie the 1031 crust that sits 30 to 50cm above the ground. Soft new windslabs are developing in the alpine where up to 60cm can be found over the 1127 wind effect and the 1031 facet crystals are 40 to 50 cm above ground.

Weather Forecast

The skies will clear Sunday morning and winds have already begun to slack and shift to the NW. The more stable pattern that we are entering into will see temperatures drop to -10 to -15 values at treeline for the 3 day period at least. Watch for wind speeds to increase in to the moderate range for Monday.

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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