Avalanche Forecast

Archived

Mar 1st, 2023–Mar 2nd, 2023

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

6am update: The wind has arrived. And there is a ton of new snow for it to blow around. Deep, fresh wind slabs will be reactive today. The new load will stress deep instabilities that have potential to produce very large avalanches.

Confidence

Moderate

Avalanche Summary

Wind slabs have been reactive lately and are expected to continue. Natural wind slab avalanches up to size 2 and wind-triggered loose dry up to size 1.5 were reported in the White Pass area on Tuesday. On Monday, a size 1.5 skier-triggered wind slab was reported in this MIN from Fraser. We really appreciate you for sharing!

Our field team recently observed a large natural wind slab avalanche that stepped down to a deeper weak layer in the Paddy Peak area, likely during the outflow winds on the weekend.

Snowpack Summary

30-40 cm of recent low density storm snow sits over firm, old, wind-hammered surfaces. If the wind picks up on Thursday, all this fresh snow is available to blow around and wind slabs are likely to form in lee terrain features.

In the mid snowpack, a couple of buried crusts have been associated with overlying surface hoar on north to east aspects as high as 1700 m, buried around 50 and 90 cm deep. Recent large avalanches are suspected to have run on the deeper of the two layers.

Weather Summary

Wednesday night

5-10 cm of new snow. Moderate southwest wind. Alpine low -12 ºC.

Thursday

Cloudy with isolated flurries. Moderate southwest wind. Alpine high -10 ºC.

Friday

A mix of sun and cloud with isolated flurries. Light variable wind. Alpine high -15 ºC.

Saturday

A mix of sun. Light to moderate easterly wind. Alpine high -18 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid the alpine during periods of heavy loading from new snow wind and/or rain.
Avoid freshly wind loaded terrain features.
Wind slabs are most reactive during their formation.
Seek out sheltered terrain where new snow hasn't been wind-affected.
Be mindful that deep instabilities are still present and have produced recent large avalanches.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.