Date issued

Apr 1, 2018 - 4:00 PM

Valid until

Apr 2, 2018 - 4:00 PM

Prepared by

tim haggarty

Some decent propagation in wind loaded start zones on Mt Bosworth during avalanche control today. Winds are shifting to the east as of publishing: new windslabs in some different locations may form for Monday.

Regular season
Monday - April 2, 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.

Tuesday - April 3, 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

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.

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.

Wednesday - April 4, 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

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.

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?

The new snow Friday arrived with strong SW winds and reports vary concerning the extent of the wind effect. Some good propagation was seen in the wind loaded portions of start zones with avalanche control. East winds Monday should redistribute snow.

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

Avalanche Problem 2: Persistent Slabs

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

This crust has given several groups a surprise over the last while. Be suspicious of solar terrain and recognize that the bond to this crust will vary with subtle changes in slope aspect and angle.

Travel and Terrain Advice
  • Be cautious with convexities and steep slopes on solar aspects.

Avalanche Summary

Avalanche control work over the last two days on Mts Bourgeau, Whymper and Bosworth produced avalanches up to sz 2.5. These were limited to the recent storm snow 15 to 50cm deep with wind loading contributing to depths. On Mt Bosworth today, crowns up to 80m wide allowed slabs to entrain enough mass in steep tracks to run 2/3 path.

Snowpack Summary

Friday's storm brought 15-40cm with moderate S and W winds creating wind slabs in the alpine and into exposed areas at treeline. The March 15 suncrust is down 25-50cm on south east through west aspects and has been sensitive to skier triggering over the last few days. The mid- pack land basal layers have been dormant for the past while.

Weather Forecast

A low slipped south of the forecast area pushed by an arctic front over the prairies. 5 cm of snow is expected overnight while winds are shifting to the east and are expected to pick up to the strong range at mountain top as the polar air pushes west bringing a cold night and dry, cloudy day. Expect a return to the SW flow and flurries late 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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