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Avalanche Forecast

Archived

Feb 10th, 2023–Feb 11th, 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 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.

Fresh flurries and recent snow are being impacted by the wind. Be most suspicious of deeper, loaded pockets around sharp changes in terrain.

Confidence

Moderate

Avalanche Summary

With the field team back in White Pass we received preliminary observations on Friday of thin, wind slabs reactive to riders and failing naturally with increasing wind from the southwest.

As we track a persistent layer deeper in the snowpack, the most recent reports are now over a week old when a couple of large (size 2-3) persistent slab, human-triggered and natural avalanches occurred near ridgetops in north-to-northeast alpine terrain. These avalanches showed 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 share your observations with the Mountain Information Network!

Snowpack Summary

The wind has impacted 30-40 cm recent snow, this pressed snow covers a crust up to 1700 m and wind-pressed surfaces at higher elevations.

Our field team continues to track a persistent layer of surface hoar and/or facets 50-100 cm deep, found on north and east aspects at upper treeline areas and higher. This layer has not produced any recent avalanches in the region and producing more stubborn results or non-results in snowpack recently.

Weather Summary

Friday night

Overnight flurries, 5-10 cm by Saturday morning. South-southwest wind gusting to 60 km/hr. Treeline low temperature -16 C.

Saturday

Flurries through the day, 5-15 cm accumulation by 4 pm. Strong southwest wind 40-60 km/hr. Treeline high temperature -7 C.

Sunday

Flurries starting late Saturday, 5-10 cm through Sunday afternonn. South wind 30-50 km/hr. Treeline high temperature -6 C.

Monday

Mostly cloudy with isolated flurries, 5 cm through the day. Southwest wind easing to light. Treeline high temperature -8 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • 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.

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.