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Archived

Avalanche Forecast

Dec 17th, 2023–Dec 18th, 2023
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Start with small slopes, and gather information before entering committing terrain.

Continue to be wary of a buried layer of surface hoar. The crust that was shielding it is getting weaker.

Confidence

Moderate

Avalanche Summary

On the weekend the only reported avalanches were loose in steep terrain, and wind slabs and cornices controlled by explosives. These avalanches were all small.

The surface hoar continues to cause concerning results in snowpack tests, and shows signs of instability like whumpfs and shooting cracks. Despite a lack of avalanche observations, we presume that large, human triggered avalanches are still possible in areas where the crust over it is thin or non-existent.

Snowpack Summary

10-15 cm of recent snow has been redistributed by moderate southwest wind. This sits on old wind slabs, and sun crusts on steeper south aspects, and in areas sheltered from the wind, 5-30 mm surface hoar.

Down 30-50 cm a 5-15 cm thick, frozen crust exists. It has been observed up to 2350 m, but it is starting to break down at treeline and above, where it is thinner. A concerning layer of surface hoar buried in early December is 60-90 cm deep at treeline and above.

The lower snowpack is generally faceted, but is also moist in some areas in the south end of the forecast area.

Average treeline snowpack depths are between 80 and 150 cm. Snowpack depth tapers rapidly with elevation.

Weather Summary

Sunday Night

Mostly clear. No new snow expected. Light southwest ridgetop wind. Treeline high around 2°C with above freezing layer.

Monday

Mostly cloudy. Possible trace of snow expected. Light to moderate south ridgetop wind. Treeline temperature around 2°C with above freezing layer.

Tuesday

Cloudy. 2-5 cm of snow expected. Light to moderate south or southeast ridgetop wind. Treeline temperature around -3°C with alpine temperature inversion.

Wednesday

Cloudy. 5-10 cm of snow expected. Light to moderate southwest ridgetop wind. Treeline temperature around -1°C with alpine temperature inversion.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Use conservative route selection and resist venturing out into complex terrain.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • Approach lee and cross-loaded slopes with caution.

Avalanche Problems

Persistent Slabs

A persistent weak layer of surface hoar is buried down 60-90 cm in the snowpack. A frozen crust was reducing the chance of triggering this layer, but it has started to break down and get weaker.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1.5 - 2.5

Wind Slabs

Potentially most reactive with above 0 temperatures around treeline, in areas where windslab sits on a layer of weak, feathery surface hoar crystals buried in mid December.

Aspects: North, North East, East, North West.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 2