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Avalanche Forecast

Archived

Mar 22nd, 2023–Mar 23rd, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Below Threshold.

Regions

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New snow and wind will form new softer wind slabs that will be easy to trigger where they are sitting on old hard surfaces or crusts.

Deeper instabilities in the snow could still be triggered from thin and rocky snowpack areas.

Confidence

Moderate

Avalanche Summary

Old large avalanches can still be seen in many areas of the Haines pass, but no new avalanches have been reported since the weekend.

On Sunday, a suspected skier triggered avalanche was reported. This was a size 1 storm slab avalanche that likely occurred on Saturday.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

5-15 cm of new snow is now sitting on snow from last week's storm that delivered 50 cm of new snow to both passes. It has been heavily wind affected in the alpine, below 1300m the new snow is resting on a crust. In sheltered northerly aspects there is up to 30 cm of soft snow still hiding from the wind.

A buried weak layer of surface hoar can be found about 80-140 cm deep in Haines Pass. This layer is most prominent on northerly slopes sheltered from the wind. On other aspects, this layer is a hard melt-freeze crust with weak facets around it. This layer has been most problematic in alpine terrain. The remainder of the middle of the snowpack is consolidated and strong.

Weak faceted grains are found near the base of the snowpack, particularly in thin snowpack areas and a thick melt freeze crust is directly on the ground in many inland areas.

Weather Summary

Wednesday Night

Cloudy with snowfall, 5 to 10 cm of accumulation. Strong easing to moderate south through to southeast sustained ridgetop winds. Alpine temperature low -8°C. Freezing levels valley bottom.

Thursday

Cloudy with snowfall, 5 to 10 cm of accumulation. Light south ridgetop winds. Alpine temperature high -5°C. Freezing levels rising to 600 m by mid day.

Friday

Cloudy with afternoon clearing, isolated very light flurries, trace to 1 cm of accumulation. Light south ridgetop winds. Alpine temperature high -5°C. Freezing levels rising to 600 m by mid day.

Saturday

Cloudy with afternoon clearing, isolated very light flurries, trace to 1 cm of accumulation. Light south ridgetop winds. Alpine temperature high -6°C. Freezing levels rising to 400 m by mid day.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be carefull around freshly wind loaded features.
  • Make observations and assess conditions continually as you travel.
  • Watch for areas of hard wind slab on alpine features.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.