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Avalanche Forecast

Archived

Dec 5th, 2020–Dec 6th, 2020

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

Regions

Sea To Sky.

As you transition from melt-freeze conditions to dry snow, lookout for wind-loaded pockets in lee features. And the possibility of wet loose avalanches will persist where snow is moist or wet.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

SATURDAY NIGHT: Increasing cloud and wet flurries / Moderate, southwest ridgetop wind / alpine low temperature -1 / Freezing level 1100 m.

SUNDAY: Cloudy with flurries; up to 10 cm / Moderate, increasing southwest ridgetop wind / alpine high temperature -2 / Freezing level 1400 m.

MONDAY: Snow; 30-45 cm / Strong, southwest ridgetop wind / alpine high temperature -2 / Freezing level 2100 m.

TUESDAY: Snow and flurries; 10-15 cm / Moderate, gusty southwest ridgetop wind / alpine high temperature -2 / Freezing level 2000 m.

Avalanche Summary

No new avalanches were reported on Thursday or Friday, however pinwheeling on steep south and west aspects was reported.

Last Wednesday, a natural widespread wet loose avalanche cycle up to size 3 occurred. A cornice failure size 1.5 also occurred triggering a small surface slab on the slope below.

Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! Sending out a big thank you to the already submitted MIN's this season. Thanks everyone!

Snowpack Summary

Recent sun and warm air well into the alpine had the greatest impact on the upper snowpack. A melt-freeze crust is found on most slopes. At upper elevations on more shaded slopes where dry snow prevails, wind slabs have formed in lee features. Surface hoar growth has been observed in sheltered areas at treeline and below.

The snowpack depth varies with elevation. Below treeline 30 to 70 cm, 80 to 100 cm near treeline, and around 150 cm may be found in the alpine.

The mid to lower snowpack contains a series of crusts, the most notable of which is also the deepest, sitting just above the ground at elevations above 1500 m. This crust may have a thin overlying layer of weak faceted grains and/or surface hoar crystals, especially in sheltered areas around treeline. There is uncertainty as to whether these layer will be a concern going forward. 

Terrain and Travel

  • Approach lee and cross-loaded slopes with caution.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid steep slopes when air temperatures are warm, it is raining, or solar radiation is strong.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.