Avalanche Forecast

Northwest Coastal

Date issued

Mar 25, 2018 - 4:44 PM

Valid until

Mar 26, 2018 - 2:00 PM

Prepared by

cgarritty

Avalanche danger will increase over the day as the next storm pulse brings heavy snow, strong winds, and rising freezing levels.

Regular season
Sunday - March 25, 2018
Alpine

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.

Treeline

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.

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.

Monday - March 26, 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.

Tuesday - March 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

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: Storm Slabs

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

Heavy snowfall is expected to pair with strong winds to create touchy new storm slabs over Sunday night and Monday. Very large avalanches may result if storm slabs release over the melt-freeze crust or surface hoar that is already 30-60 cm deep.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • Avoid overhead exposure during periods of heavy loading from new snow, wind.
  • Rising freezing levels may lead to loose wet avalanches. Use extra caution if snow becomes moist.

Avalanche Summary

Reports from Saturday showed ski cutting in the Bear Pass area producing both slab and loose dry avalanches to size 1.5. Slabs failed all the way down to the melt-freeze crust buried 60 cm deep at treeline on north aspects. No new avalanches were reported in the south of the region. Poor visibility led to limited observations throughout the region.

On Saturday, the strong westerly winds were responsible for triggering a couple of wind slabs up to size 1.5 from north-easterly aspects in the alpine.
On Friday and MIN reported a rider triggered wind slab avalanche size 1.5 from a southwest aspect. The person rode out of the avalanche and the crown was reportedly 35 cm deep. Friday also saw a natural cycle up to size 2.5 in the recent storm snow.

Snowpack Summary

The past week of stormy weather brought 30-60 cm of new snow to the region. Strong easterly winds initially redistributed the new snow onto leeward aspects, forming thick wind slabs. More recent and forecast strong southwest winds are likely to continue building wind slabs on north through east aspects.

Beneath the wind effect, the new snow overlies a plethora of old snow surfaces, including a layer of surface hoar existing on high shaded aspects as well as a melt-freeze crust on all aspects at treeline and below.

Deeper in the mid-pack, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist from mid- and late-February and a surface hoar/ crust layer from January is buried around 150 to 200 cm. Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north. These buried layers are currently dormant.

Weather Forecast

Sunday night: Flurries bringing approximately 10 cm of new snow. Moderate to strong southwest winds.

Monday: Continuing periods of snow bringing approximately 20 cm of new snow. Strong southwest winds, gusting to extreme at high elevations. Freezing level to 900 metres with alpine high temperatures around -2.

Tuesday: Mainly cloudy with continuing scattered flurries 3-5 cm of new snow. Strong southwest winds. Freezing level to 800 metres with alpine high temperatures around -3.

Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate to strong west winds. Freezing level to 800 with alpine high temperatures around -3.

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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