Avalanche Forecast

Sea To Sky

Date issued

Mar 10, 2018 - 4:02 PM

Valid until

Mar 11, 2018 - 3:00 PM

Prepared by

mbender

As the day warms up and the surface snow starts to melt, the avalanche danger will gradually rise.

Regular season
Saturday - March 10, 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.

Sunday - March 11, 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 - March 12, 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: Persistent Slabs

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

A layer of surface hoar, sugary facets, and/or crust is buried 50-100 cm deep and has produced widespread whumpfing, concerning snowpack test results, and a few large remotely triggered avalanches. Upper treeline elevations are the greatest concern.

Travel and Terrain Advice
  • Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.
  • Use conservative route selection while travelling at treeline elevations.
  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Storm Slabs

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

Recent snow and southwest winds have built storm and wind slabs. Expect to see loose wet avalanches as the sun comes out and the freezing level rises.

Travel and Terrain Advice
  • Be cautious as you transition into wind affected terrain.
  • Extra caution needed around cornices with current conditions.
  • Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Avalanche Summary

On Saturday there were several size 2.5 natural persistent slab avalanches reported. These were suspected to have run in the previous 24hours and were observed on northwest to east aspects between 1900 and 2000m. On Friday there were reports of a several explosives and naturally triggered storm slab avalanches size 1.5-2 on a variety of aspects that entrained the storm snow only. There were also a few skier triggered size 1-1.5 storm slab avalanches on northeast aspects and a few explosives controlled cornice releases to size 1.5.

Snowpack Summary

Recent new snow has been redistributed by by strong west and south winds. This new snow sits on a sun crust on steep south-facing slopes, cold dry snow on northerly aspects, and wind affected snow at upper elevations. The surface snow is reported to be moist on all aspects to 1800m and to mountain top on solar aspects.

Last week's storms buried a weak layer composed of soft facets, surface hoar, and/or crust that is roughly 50-100 cm below the surface. This layer has produced whumpfing, sudden results in snowpack tests, and some remotely triggered avalanches. Lots of the activity has been on buried surface hoar on north aspects at upper treeline elevations. The snowpack is well settled and strong beneath this interface.

Variable winds in the past month have produced cornices on many ridgelines. 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

SUNDAY: Mix of sun and cloud / Light south wind / Alpine temperature 3 / Freezing level 2000m

MONDAY: Mix of sun and cloud / Light southeast wind / Alpine temperature 5 / Freezing level 2200m

TUESDAY: Cloudy with flurries or rain showers / light to moderate south wind / Alpine temperature 4 / Freezing level 2100m

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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