Avalanche Forecast

Archived

Mar 2nd, 2023–Mar 3rd, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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 possible, human triggered probable.

Below Treeline

Below Threshold.

Regions

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

Wind slabs will remain triggerable by riders Friday. Shooting cracks in stiffened or drifted snow are good indicators of reactive wind slab. Be mindful that deep instabilities still exist and have recently produced very large avalanches.

Confidence

Moderate

Avalanche Summary

Since the storm cleared up on Thursday, our field team has observed a natural avalanche cycle up to size 3 from the highway. We suspect that some of these may include step-downs to buried weak layers.

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 last weekend.

Snowpack Summary

30-50 cm of recent snow has been stiffened at the surface and transported into wind slabs by moderate winds at upper elevations. At lower elevations, the recent snow has settled in Thursday's mild temperatures.

In the mid snowpack, a couple of crusts buried 60+ cm and 100+ cm deep have been problematic on north to east aspects as high as 1700 m, where they are covered in an overlying layer of weak surface hoar crystals. Recent large avalanches are suspected to have run on the deeper of the two layers. On the bright side, recent snowpack tests by our field team suggest that these layers are beginning to strengthen and bond.

Weather Summary

Thursday night

Flurries bringing up to 5 cm. Moderate southerly wind. Alpine low -12 ºC.

Friday

Cloudy with sunny breaks. Light northeast wind picking up in the evening. Alpine high -15 ºC.

Saturday

A mix of sun and cloud. Moderate to strong northeasterly outflow wind. Alpine high -19 ºC.

Sunday

Mostly sunny. Strong northeasterly outflow wind. Alpine high -21 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be especially cautious as you transition into wind affected terrain.
Stay off recently wind loaded slopes until they have had a chance to stabilize.
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.