Date issued

Apr 6, 2018 - 4:00 PM

Valid until

Apr 7, 2018 - 4:00 PM

Prepared by

tim haggarty

A skier triggered avalanche yesterday afternoon highlights the serious nature of the March 15 persistent slab problem. Watch for increasing avalanche hazard through the weekend with incoming new snow.

Regular season
Saturday - April 7, 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

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.

Sunday - April 8, 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

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 9, 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

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?

Dig down to test the bond to the Mar 15 crust, bearing in mind that the bond can vary significantly with subtle changes in slope aspect and steepness. Forecasters suspect this problem is developing with  faceting on the crust due to recent cold temps

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

Avalanche Problem 2: Wind Slabs

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

Expect to encounter smaller windslabs in the alpine. They range from 20-40cm thick and have been decreasing in sensitivity over the last couple of days. Watch for the incoming storm to establish new slabs Saturday and Sunday.

Travel and Terrain Advice
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Avalanche Summary

Visitor Safety responded to Sentinel Pass for a skier accidental avalanche reported by the involved party via In-reach at approx 1700hrs April 5. Avalanche failed on March 15 crust persistent layer that has been sensitive to skier triggering for a couple of weeks ... 20-50cm deep at 2575m ,SE aspect, 200mx200m. Impressive save by party members.

Snowpack Summary

Trace amounts of new snow in the past 18 hours. Last week's storm brought 15-40cm with moderate S and W winds creating wind slabs in the alpine. 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.

Weather Forecast

Continued flurries overnight Friday with more significant snowfall expected on to start mid afternoon Saturday with and increase in temperatures. Expect both the new snow and the increasing temperatures to lead to an increase in the avalanche hazard. Further increases in temperature can be seen in long term forecasts, a significant change to watch.

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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