Avalanche Forecast

Archived

Feb 5th, 2023–Feb 6th, 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 unlikely, human triggered possible.

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.

carefully assess snowpack conditions as you gain elevation. A tricky weak layer exists in the alpine and new wind slabs are likely to increase in size and reactivity.

Use

Confidence

Moderate

Avalanche Summary

This MIN discusses new wind slab formation. We expect wind slabs to increase in size and reactivity.

A couple of large (size 2-3) persistent slab, human-triggered and natural avalanches were reported last week. These avalanches occurred near ridgetops in north-to-northeast alpine terrain. These avalanches have shown an impressive capability to propagate across large distances. Here is a link to the most recent human-triggered size 3 avalanche.

If you are out in the backcountry please consider filling out a Mountain Information Network report.

Snowpack Summary

New snow continues to accumulate with southwest winds forming wind slabs on north and east aspects. New snow is resting on a variety of wind-affected surfaces and crusts with small surface hoar in places in the alpine. Below roughly 1700 m a widespread 5-10cm melt-freeze crust is present at or near the surface.

A concerning persistent weak layer of surface hoar and/or facets is 50-80 cm deep and exists on north facing alpine features.

Check out this MIN from our field team to learn more.

Weather Summary

Sunday Night

Cloudy with up to 10cm of new snow possible. Moderate to strong southerly winds and a low of -5 at 1500m.

Monday

Increasing cloud throughout the day with up to 5cm of new snow expected. Light to moderate southwest winds and a high of -5 at 1500m.

Tuesday

A mix of sun and cloud with up to 5cm of new snow expected. Moderate south winds and a high of -5 at 1500m.

Wednesday

A mix of sun and cloud with flurries bringing a few centimeters of new snow. Light to moderate southwest winds and a high of -8 at 1500m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

In times of uncertainty conservative terrain choices are our best defense.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Persistent slabs have potential to pull back to lower angle terrain.
Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.

Problems

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.

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.