Date issued

Apr 13, 2018 - 3:00 PM

Valid until

Apr 14, 2018 - 2:00 PM

Prepared by

mike.koppang

New windslabs have/are developed in alpine terrain that skiers should pay close attention too. Choose supported features and rein yourself in a little.  Watch for the affects of solar radiation on solar aspects later in the day.

Regular season
Saturday - April 14, 2018
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

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.

Sunday - April 15, 2018
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 - April 16, 2018
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: Wind Slabs

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

Windslabs up to 20cm thick in lee and crossloaded features.  These slabs will build overnight on Friday and get a little bit larger and stiffer.  Use Caution.

Travel and Terrain Advice
  • Avoid lee and cross-loaded terrain near ridge crests.
  • Give cornices a wide berth when travelling on or below ridges.

Avalanche Problem 2: Persistent Slabs

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

Lots of variability on this interface down 50cm.  This is a persistent slab that is overlying a thick suncrust that was buried on solar aspects on March 15th.

Travel and Terrain Advice
  • Minimize exposure to sun exposed slopes when the solar radiation is strong.
  • Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

Avalanche Problem 3: Cornices

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

Cornices are large and looming and become weak with daytime heating. They may collapse and trigger an avalanche on the underlying slopes.

Travel and Terrain Advice
  • Cornices become weak with daytime heating, so travel early on exposed slopes.

Avalanche Summary

One size two wet slab was observed on the EEOR later in the day on Friday but otherwise, only isolated pinwheeling on solar aspects.

Snowpack Summary

SW winds increased in alpine overnight and into the morning building windslabs up to 20cm thick in lee features. Recent snow is overlying a supportive MFC that is 4-6cm thick up to 2200m. All aspects were moist up to 2000m by midday and moist snow suspected up to the peaks on solar. Hard sudden planar  results on the March 15th crust down 50cm at 2200m on a SE aspect at treeline.  Start early when travel on the crusts is good and fast

Weather Forecast

Winds out of the SW are forecast to increase overnight further loading and building on the current windslabs.  Conditions will be a mix of sun and cloud with daytime highs are -7C in the alpine.  Pay attention to the sun, solar radiation is strong at this time of year and solar aspects will quikly become less stable as temperatures warm up.  These decreases will be most apparent in thin, steep, rocky solar terrain.

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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