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Avalanche Forecast

Archived

Nov 19th, 2023–Nov 20th, 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.

Strong wind and new snow will keep the avalanche hazard elevated. Watch for pockets of wind slab above tree line and in the alpine.

Early season hazards exist everywhere.

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

Confidence

Low

Avalanche Summary

No new observations on Sunday, but visibility was poor. I suspect there was some activity in the alpine due to the strong winds.

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.

Snowpack Summary

The height of snow at treeline is ~90cm. A thin crust on steep solar aspects has been buried by 5-10cm of new 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

Cloudy with sunny periods for Monday with SW winds up to 40 kph and an alpine high of -1. Freezing level expected to rise up to 1200m. No snow is forecasted.

Tuesday freezing levels will rise, with a pocket of warm air sitting between 1800-2500m. Winds are expected to be 40-65kph from the West.

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

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • 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.

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.