Avalanche Forecast

Sea To Sky

Date issued

Mar 20, 2018 - 5:34 PM

Valid until

Mar 21, 2018 - 2:00 PM

Prepared by

ghelgeson

It is a good time to be traveling in the mountains, but remember that low danger does not mean no danger. Loose wet avalanche activity should be limited Wednesday, but stubborn old wind slabs and large cornices demand our respect.

Regular season
Wednesday - March 21, 2018
Alpine

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.

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.

Thursday - March 22, 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.

Friday - March 23, 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?

It is a good time to be traveling in the mountains. Increased cloud cover should put the brakes on loose wet activity. Use normal caution and be aware that small wind slabs near ridge crest may be sensitive to human triggering.

Travel and Terrain Advice
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Give cornices a wide berth while on or below ridges.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Avalanche Summary

Avalanche activity on Monday was limited to surface facets and surface hoar sluffing away in steep terrain.

A few skier triggered soft slabs size 1 to 1.5 were reported from west facing alpine terrain Sunday. These were likely running on the mid-March crust.

Saturday's reported avalanche activity was limited to sluffing and snowballing in steep terrain.

There was a rather anomalous size 3.5 that was seen on the Cheakamus Glacier from Whistler last Thursday. We don't have details on the failure plane of this avalanche, but it may have run on the mid-February crust.

Snowpack Summary

A new crust exists on the surface on solar aspects at all elevations. High elevation polar aspects (those facing north and east) continue to hold dry snow, this is also where trophy surface hoar up to 15 mm in size has spotted on the surface.

5 to 20 cm of wind distributed snow fell last week which came to rest on the mid-March crust on all but high elevation north aspects.

50 to 100 cm below the surface is a combination of facets, surface hoar, and/or crust known as the mid-February layer. This interface has not been active recently, but it does continue to produce resistant planar results in snowpack tests.

The mid and lower snowpack is strong and well settled.

Variable winds in the past month have built up cornices on many ridgelines. They will become touchier as daily temperatures rise and when they are subject to the strong early spring sun on clear days.

Weather Forecast

Wednesday looks to be the last day of rather vanilla weather before a significant change Thursday. The pattern is incredibly dynamic as we move towards the weekend, this is a great time to check out our Mountain Weather Forecast (link below) if you are curious. Suffice to say that Wednesday does not offer much change, but then significant rain/snow and plenty of wind is in store, at least through Friday.

WEDNESDAY: Broken cloud cover with some clearing in the late afternoon, freezing level beginning at 800 m rising to 1400 m, trace of precipitation during the day, 2 to 10 mm of precipitation expected Wednesday night.

THURSDAY: Overcast, freezing level starting at 1500 m, lowering to 800 m by sundown, strong southerly wind, 15 to 20 mm of precipitation.

FRIDAY: Scattered cloud cover, freezing level beginning at 500 m rising to 900 m, light southerly wind, 3 to 5 mm of precipitation possible.

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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