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Avalanche Forecast

Archived

Dec 14th, 2023–Dec 15th, 2023

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

Regions

McBride.

Recent storm snow and buried weak layers may be reactive to human triggering, especially above treeline.

In times of uncertainty conservative terrain choices are our best defense.

Confidence

Moderate

Avalanche Summary

On Wednesday, a few isolated wind slabs were seen up to size 1.

Several skier-triggered persistent slab avalanches up to size 2.5 were reported earlier this week. They failed on weak layers comprised of surface hoar and or facets 40-70 cm. Check out this MIN from the adjacent region. It paints a clear picture.

Human-triggered persistent slabs remain the primary concern.

Snowpack Summary

10 to 20 cm of new snow has buried old wind-affected snow, sun crusts on steep south aspects and surface hoar. Approximately 25 to 40 cm down exists a rain crust that has been observed to ridgeline in most areas.

A concerning layer of surface hoar is now buried 50-80 cm deep. This layer has recently been reactive to human triggering above 2100 m.

The lower snowpack is a mix of rounded and faceted grains. A hard crust may be found near the ground.

Treeline snowpack depths are variable and generally range between 100 to 150 cm. Snowpack tapers rapidly as you move lower in elevation.

Weather Summary

Thursday Night

Mix of cloud and clear. Ridgetop wind 10-15 km/h from the southwest and temperatures near -7 C. Freezing levels valley bottom.

Friday

Cloudy with sunny periods and isolated flurries 2-5 cm. Ridgetop wind 20 to 45 km/h and temperatures near -2 C. Freezing levels valley bottom.

Saturday

Mix of sun and cloud. Isolated flurries 2-5 cm. Ridgetop temperatures near -2 and freezing levels valley bottom. Possible weak alpine temperature inversion.

Sunday

Mix of sun and cloud. Ridgetop wind 15 to 25 km/h from the west and temperatures near 0 C. Freezing levels valley bottom. Alpine temperature inversion.

More details 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.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.

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.