Avalanche Forecast

Lizard Range and Flathead

Date issued

Mar 25, 2018 - 4:47 PM

Valid until

Mar 26, 2018 - 2:00 PM

Prepared by

cgarritty

Strong winds will maintain touchy conditions on Monday. Keep seeking out supported lines in sheltered areas while the storm snow settles and bonds.

Regular season
Sunday - March 25, 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.

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

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.

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

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?

Increasingly strong southwest winds are set to press and redistribute our new snow into reactive new wind slabs over Sunday night and Monday. Slabs may also be reactive in steeper, sheltered areas where the recent snow sits on crust or surface hoar.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Wind slabs may be more reactive where they sit on a buried crust or surface hoar interface
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Avalanche Problem 2: Cornices

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

Large looming cornices exist across ridgelines. Cornices are unpredictable and demand respect. They're more likely to fail during wind events or when the sun comes out.

Travel and Terrain Advice
  • Give cornices a wide berth when travelling on or below ridges.
  • Pay attention to overhead hazards like cornices which could trigger a slab from the slope below.

Avalanche Summary

Cornice control on Saturday work gave numerous size 1-2 avalanches on north through southeast ridgelines. above 1900m. The cornice failures produced mostly loose dry avalanches from the slopes below with a few smaller slabs only releasing in the storm snow.
On Friday, numerous natural storm slab avalanches were reported from North aspects above 1700 m.
Periods of sunshine forecast for Sunday could trigger a round of natural slab avalanches and loose dry/wet avalanches.

Snowpack Summary

Up to 50 cm of recent storm snow will initially have a poor bond to the plethora of old snow surfaces including a melt-freeze crust on sunny aspects and all aspects below 1600 m, surface hoar on north aspects above 1600 m. Wind slabs are building on most aspects due to the changing winds and overhanging cornices exist along ridgelines.

Deeper in the snowpack, the mid-December and late-November weak layers are composed of crusts and sugary facets, which are down 150-300 cm. These layers are currently dormant.

Weather Forecast

Sunday night: Scattered flurries bringing a trace to 5 cm of new snow. Moderate to strong southwest winds.

Monday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Strong southwest winds. Freezing level to 1300 metres with alpine high temperatures around -5.

Tuesday: Cloudy with scattered flurries bringing around 2 cm of new snow, increasing overnight. Strong to extreme southwest winds. Freezing level rising to 1800 metres after a poor overnight refreeze. Alpine high temperatures around -1.

Wednesday: A mix of sun and cloud with continuing scattered flurries bringing a trace to 5 cm of new snow. Moderate westwinds. Freezing level to 1600 metres 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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