Date issued

Nov 26, 2017 - 8:00 AM

Valid until

Nov 27, 2017 - 8:00 AM

Prepared by

ian gale

High freezing levels and heavy precipitation are forecast for today.  Rain at treeline and below will destabilize the snowpack.

Regular season
Sunday - November 26, 2017
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 - November 27, 2017
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.

Tuesday - November 28, 2017
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?

Heavy snowfall with wind today will build a touchy storm slab. The Nov 23rd crust will be a good bed surface for avalanches to run on. Avalanches may run far on top of this layer.

Travel and Terrain Advice
  • The new snow will require several days to settle and stabilize.
  • Use caution in lee areas. Recent wind loading have created wind slabs.

Avalanche Problem 2: Wet Slabs

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

Dry surface snow is insulating a rain-saturated wet slab that extends almost to the ground. This is a snowpack weakness that will only heal with cold.  Rain at treeline and below will destabilize the snowpack further.

Travel and Terrain Advice
  • Use extra caution on slopes if the snow is moist or wet.
  • Avoid steep, open slopes.

Avalanche Summary

Three natural size 2.5's were observed from high Alpine start zones yesterday along the highway, likely triggered by recent snowfall and windloading at ridgetop. Avalanches, once initiated, are able to run far on the Nov 23rd crust.

Snowpack Summary

25cm of dry snow is beginning to bond to a breakable crust. Below the November 23 crust sits a weak rain-saturated snowpack. If you take your skis off, you'll likely be standing in a hole up to your waste. Strong winds during the last storm created isolated pockets of wind slab in the alpine on northerly features. October 31 crust is down 100cm.

Weather Forecast

A significant storm today will bring up to 25 cm of snow and freezing level rising above 2000 meters.  Winds are expected to be from the South at 40 k/hr.  High freezing levels translates to heavy rainfall again below treeline.  The stormy weather pattern will continue through the week and freezing levels are forecast to drop and stay around 1000m

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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