Avalanche Forecast

Purcells

Date issued

Mar 15, 2018 - 4:37 PM

Valid until

Mar 16, 2018 - 2:00 PM

Prepared by

jmcbride

There is some snow on the way but forecasted amounts are not expected to have much impact on hazard ratings.  Watch for pockets of lingering wind slab at upper elevations.

Regular season
Friday - March 16, 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

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.

Saturday - March 17, 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

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.

Sunday - March 18, 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.

Avalanche Problem 1: Wind Slabs

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

Pockets of reactive wind slab can still be found in leeward areas in the alpine. In the northern part of the region, these slabs may be sitting on a layer of surface hoar on shaded aspects at treeline as well.

Travel and Terrain Advice
  • Give cornices a wide berth when travelling on or below ridges.
  • Watch for wind loaded pockets near ridge crests and roll overs.

Avalanche Summary

Numerous wet loose avalanches were observed in the region to size 2.5 over the past several days on sunny aspects. As well as both skier and sledder triggered wind slabs up to size 1.5 on south east to west aspects

On Sunday we received reports of a skier caught in a size 2.5 avalanche in the north of the region. The slab was 20-50 cm thick and started on a steep north east aspect immediately below ridge crest at 2300m. See the MIN post for more details.

Snowpack Summary

A light dusting of new snow now covers a crust on all but high elevation northerly aspects which still hold loose, dry snow above a generally well-settled snow pack.

A couple of layers buried in mid-late February (down around 40-100 cm) have shown limited reactivity of late. Persistent slabs have been triggered on shady aspects, where surface hoar and/or facets exist. Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets also linger at the base of the snowpack.

Weather Forecast

TONIGHT: Flurries. Accumulation 5-10 cm. Ridge wind light, southwest. Alpine Temperature near -5. Freezing level 700 m.

FRIDAY: Cloudy, light flurries. Accumulation trace. Ridge wind light, northeast. Alpine Temperature near -6. Freezing level 1700 m.

SATURDAY: Mostly cloudy, flurries. Accumulation 5-10 cm. Ridge wind light, east. Alpine Temperature near -4. Freezing level 1600 m.

SUNDAY: Mostly cloudy, light flurries. Accumulation 2-6 cm. Ridge wind light, northwest. Alpine Temperature near -5. Freezing level 1500 m.

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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