Avalanche Forecast

Sea To Sky

Date issued

Feb 27, 2018 - 3:49 PM

Valid until

Feb 28, 2018 - 2:00 PM

Prepared by

ghelgeson

This forecast is based around 2 to 10 cm of snow Wednesday and continued strong wind. If snow totals exceed 15 cm in the afternoon then danger ratings will be one step higher at all elevations. Seek out wind sheltered terrain!

Regular season
Tuesday - February 27, 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.

Wednesday - February 28, 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

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.

Thursday - March 1, 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

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: Wind Slabs

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

Strong wind over the last 48 hours has formed wind slabs that may remain sensitive to human triggering. New snow and strong south/southwest wind are expected to form fresh wind slabs throughout the day Wednesday too.

Travel and Terrain Advice
  • Seek out wind sheltered terrain below treeline.
  • Avoid wind loaded terrain features, especially during periods of active loading.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.

Avalanche Summary

On Monday natural wind and storm slab avalanches to size 2.5 were observed on east/southeast facing slopes around 2000 m. A size 1.5 wind slab was skier triggered on an east facing alpine feature near ridgetop. A second storm slab was skier triggered on a northeast/east facing slope at 1900 m. Unsupported rolls at treeline were also sensitive to ski cuts producing very soft slabs 30 to 70 cm in depth.

A lot of avalanche activity was reported on Sunday as the 25 to 40 cm of recent storm snow ran on the February 22nd weak layer. Control work produced numerous loose dry storm and wind slab avalanches to size 1.5 on a variety of aspects. A size 1.5 storm slab failed naturally on a steep roll on a northeast facing slope at 1600 m while a size 2.5 natural avalanche was reported from a southeast aspect of the Miller glacier at 2250 m.

Snowpack Summary

Storm totals from the weekend are between 25 and 55 cm. This snow was subject to strong to extreme winds out of the southeast, south and southwest on Sunday and Monday which has formed fresh wind slabs that extend down to treeline. The new snow rests on the February 22nd interface which consists of old wind slabs, spotty surface hoar, facets and a sun crust on solar aspects. Reported testing on Monday continues to produce resistant planar shears at this interface which makes sense given the activity listed above. Beneath the February 22nd interface the snowpack is well settled and strong.

Variable winds in the past month have produced cornices on all aspects. They will become touchier as they grow in size, as temperatures rise, and when they are subject to the strong late-winter sun on clear days.

Weather Forecast

We are entering what looks to be a very snowy period. The Wednesday night storm has potential to be quite vigorous, and then the gift should keep on giving as the associated upper low drops south over the next few days. Weather models are converging on a solution but this is an incredibly dynamic period and the following should be taken as loose suggestions. If you are craving detail, now is a great time to click on the ACMWF link below.

WEDNESDAY: Overcast, snow level around 800 m, strong south/southwest wind, 2 to 10 cm of snow.

WEDNESDAY NIGHT: Snow level around 800 m, 10 to 25 cm of snow, strong to extreme southwest wind.

THURSDAY: Scattered cloud cover, freezing level around 1000 m, light southeast wind, trace of snow possible.

FRIDAY: Scattered cloud cover, freezing level around 1100 m, light variable wind, no precipitation expected.

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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