Avalanche Forecast

Archived

Mar 7th, 2023–Mar 8th, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Regions

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

Firm wind slabs are often stubborn to trigger so they can surprise you once you hit that weak spot. Seek out sheltered terrain in side valleys for the best riding.

Confidence

Moderate

Avalanche Summary

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.

On Friday, our field team observed natural wind slab avalanches up to size 2 and loose snow sluffing from steep alpine terrain around the White Pass.

Snowpack Summary

Outflow winds from the north have done a real number on the surface snow scouring exposed terrain, creating waves of sastrugi in more sheltered terrain, and forming wind slabs on southerly aspects. Very sheltered terrain in side valleys to the east and west of White Pass still harbour softer snow for riding.

The middle of the snowpack is very firm and settled. There is a surface hoar layer buried 60 cm (Powder Valley, Tuthsi, Paddy Peak) to 120 cm (White Pass) deep in sheltered, mostly north facing terrain features that produced some large, human-triggered avalanches in January and February.

At the base of the snowpack large sugary crystals persist.

Weather Summary

Tuesday night

Clear. Moderate northerly outflow wind. Low temperature -22 ˚C, with windchill -35 ˚C.

Wednesday

Sunny. Moderate northeasterly outflow wind. Alpine high -20 ˚C.

Thursday

Increasing cloud with flurries bringing a few cm of snow. Winds easing to light variable. Alpine inversion with a high of -10 ˚C at 1800 m.

Friday

Up to 5 cm overnight then light flurries with sunny periods. Moderate northerly wind. Alpine high -16 ˚C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

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.
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.