Avalanche Forecast

Lizard Range and Flathead

Date issued

Apr 6, 2018 - 4:37 PM

Valid until

Apr 7, 2018 - 2:00 PM

Prepared by

jmcbride

New snow and wind beginning late Saturday afternoon will increase avalanche hazard.  If however, the storm arrives earlier than forecasted, hazard ratings will also increase sooner.

Regular season
Friday - April 6, 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.

Saturday - April 7, 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.

Sunday - April 8, 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

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?

Wind slabs have been a consistent feature for several days and will continue to be an issue in exposed terrain. Shifting winds means you should look out for wind slab on almost all aspects.

Travel and Terrain Advice
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Pay attention to overhead hazards like cornices which could easily trigger slabs.

Avalanche Problem 2: Cornices

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

Cornices are reported to be large and several cornice failures have recently been noted.

Travel and Terrain Advice
  • Extra caution needed around cornices with current conditions.
  • Give cornices a wide berth when travelling on or below ridges.

Avalanche Summary

Numerous small slab avalanches have been reported in the top 10-25 cm of snow all through this week. It appears as though moderate amounts of new snow with just the right amount of wind have continuously set up thin, but touchy wind slabs in a variety of places. While these have been mostly small (size 1), a size 2 wind slab avalanche was reported near Fernie on Wednesday morning on a northeast aspect at approximately 2000 m.

Explosive control work on Friday produced wind slab and cornice releases up to size 2 in alpine terrain.

Thursday in the Elkford area, recent small (size 1) loose/dry avalanches were reported on northerly aspects while loose/wet were observed on solar aspects.

Also, cornices are large along ridgetops and were actively failing last week.

Snowpack Summary

20-30 cm storm snow sits above a variety of crusts on all but high north aspects. Wind has formed isolated slabs in lee features, and in some cases snow may be poorly bonded to the crusts.

There are some reports of a surface hoar layer roughly 80 cm deep on north aspects at treeline, but no recent avalanche activity on this layer. A layer of sugary facets around a crust exists near the bottom of the snowpack, but this layer has been inactive for some time.

Weather Forecast

TONIGHT: Mostly clear. Ridge wind light to moderate, west. Alpine temperature near -5. Freezing level valley bottom.

SATURDAY: Increasing cloud, snow beginning in the afternoon. Accumulation 5-15 cm. Ridge wind moderate to strong, south. Alpine temperature near -3. Freezing level 1000 m.

SUNDAY: Cloudy, flurries. Accumulation 5-10 cm by Sunday morning. Ridge wind moderate to strong, west. Temperature near 0. Freezing level 1800 m.

MONDAY: Mix of sun and cloud. Ridge wind moderate, west. Alpine temperature near 0. Freezing level 1800 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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