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Avalanche Forecast

Archived

Nov 18th, 2023–Nov 19th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Early Season

Regions

Glacier.

Increasing wind and new snow will gradually elevate the avalanche hazard over the day. Watch for wind slab formation in the Alpine and open areas at treeline.

Early season hazards exist everywhere.

The Winter Permit System started on Nov 16! Get your permit and know what areas are open before you venture into the backcountry.

Confidence

Moderate

Avalanche Summary

Several natural sz 2.0 avalanches were observed Friday in Lone Pine, Single Bench, Lens, Cougar Valley and Gunners 2. Daytime warming and solar input also released small point release avalanches on solar aspects.

On Thursday, the West face of Cheops produced a sz 2.0 persistent slab and several loose dry avalanches on steep North facing terrain. Artillery control (gun site verification) produced results up to sz 2.5 on steep North facing terrain on Mt. MacDonald.

Snowpack Summary

The height of snow at treeline is ~80cm. A thin crust may have formed on steep solar aspects and will be buried by the incoming snow.

The bottom of the snowpack is facetted and offers little support to the shallow snowpack, often settling and producing large "whumpfs". Snow depth increases with elevation but distribution is highly variable, expect many rocks/trees lurking at and just below the snow surface.

Weather Summary

Sunday we can expect 5-10cm of new snow with 25-40kpm Westerly winds with temps dropping down to -13 in the Alpine.

Monday, winds will drop slightly and temps begin to rebound.

Tuesday will see 30-60kpm winds in front of a small pulse of snow.

Detailed weather forecasts can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected 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.