Avalanche Forecast

Lizard Range and Flathead

Date issued

Feb 26, 2018 - 4:48 PM

Valid until

Feb 27, 2018 - 2:00 PM

Prepared by

istorm

Ongoing winds will continue to drive new windslab development. The best riding will be in wind sheltered terrain.

Regular season
Monday - February 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 - February 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

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.

Wednesday - February 28, 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: Wind Slabs

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

Touchy wind slabs can be found downwind of ridges, ribs, and cross-loaded features. In sheltered areas protected from the wind (where the best riding can be found) soft storm slabs on steeper slopes and rolls may be a concern.

Travel and Terrain Advice
  • Travel on ridgetops to avoid wind slabs on slopes below.
  • Be cautious as you transition into wind affected terrain, and avoid slopes below cornices.
  • Watch for signs of instability such as whumpfing, or cracking on small slopes.

Avalanche Summary

Numerous wind slabs up to size 2 and loose dry avalanches up to size 1.5 were reported from the Lizard Range on Monday running either naturally or triggered by skiers testing small slopes. Explosives triggered storm slabs up to size 2 on northerly aspects.

Snowpack Summary

New wind slabs are building as up to 45 cm of light dry snow fell in the past two days and is being moved around by moderate to strong westerly winds. Snow spillage from steep ground is also loading up fans. In more sheltered locations, you may encounter storm slabs or loose dry sluffing. These upper snowpack problems overlie various old surfaces including old hard wind slabs, crusts, facets and spotty surface hoar (for example February 14 surface hoar is now 60 to 80 cm below the surface).

Deeper in the snowpack, the widespread mid-December weak layer sits about 200+ cm deep. This consists of a crust, facets or surface hoar.

Near the base of the snowpack, a crust/facet layer could be awoken from a thin-spot trigger point, or with a very large load like a cornice fall.

Weather Forecast

Monday day and overnight was a period of relative calm, meaning no new snow but a moderate westerly wind kept blowing.

TUESDAY:  The next wave of snow is expected to arrive in the morning with 5 to 10 cm expected. There might be more overnight but I'd be surprised if you woke up to more than 15 cm in total by Wednesday morning. Moderate to strong westerly winds and temperatures around -5 to -10 at treeline.

WEDNESDAY & Thursday:  The weather pattern is expected to shift to a more southwesterly flow with warmer temperatures and continued bands of precipitation. Timing and intensity of these bands is uncertain but current forecasts suggest accumulations of around 5 cm per day, and freezing levels around 1300 to 1500m.

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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