Avalanche Forecast

Archived

Mar 11th, 2023–Mar 12th, 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.

Treeline

Natural avalanches unlikely.

Below Treeline

Below Threshold.

Regions

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

Don't let bluebird conditions encourage you into big terrain features. The persistent weak layer continues to be a concern at alpine elevations, where wind slabs also exist.

Keep these problems in mind as you plan your travels.

Confidence

Moderate

Avalanche Summary

On Friday several recent size 2 wind slabs were observed in the Paddy Peak area. Observers noted active wind transport still occurring with snow available for transport.

On Tuesday, a size 2.5 persistent slab avalanche was remotely triggered by skiers on a ridgetop in the alpine. The slab propagated widely on a thin, rocky southeast aspect and it stepped down to basal facets lower on the slope.

Snowpack Summary

Strong winds from the north and northeast continue to scour exposed terrain, creating waves of sastrugi, and forming wind slabs on southerly aspects. Areas north of White Pass have more loose snow available for transport. Sheltered terrain in side valleys to the east and west of White Pass still may also hold softer snow for riding.

The middle of the snowpack is very firm and settled. There is a surface hoar layer buried from 60 cm (in Powder Valley, Tutshi, Paddy Peak) to 120 cm (White Pass) deep in sheltered, mostly north facing terrain features. On other aspects this layer exists as a crust and facets. Natural and human triggered avalanches have occurred on these layers recently and it remains a concern in alpine terrain.

At the base of the snowpack large sugary crystals persist.

Weather Summary

Saturday Night

Mostly clear skies overnight. Moderate to strong northeasterly wind. No snowfall expected.

Sunday

Sunny. Strong winds easing to moderate from the northeast. Alpine high -18 ˚C.

Monday

A mix of sun and cloud with light to moderate easterly wind. Alpine high of -15 ˚C.

Tuesday

A mix of sun and cloud with light southerly wind. Alpine high of -15 ˚C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Seek out sheltered terrain where new snow hasn't been wind-affected.

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.