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Avalanche Forecast

Archived

Jan 13th, 2017–Jan 14th, 2017

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

Regions

South Rockies.

Wind effect is the critical factor. The safest, best riding may be in lower elevation terrain sheltered from the wind.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

The dominating arctic airmass will linger through the weekend with continued cold temperatures at valley bottom and a strong alpine inversion, mostly cloudy skies with some sunny periods. Saturday/ Sunday/ Monday: Mix of sun and cloud with an alpine high near -8. Ridgetop winds light from the West. Check out the full synopsis here: https://avalanche.ca/weather/forecast

Avalanche Summary

On Thursday, wind slabs up to size 1 were easily triggered by the weight of a person. Variability in the winds has been the name of the game and reactive wind slabs may be found on all aspects at upper elevations.

Snowpack Summary

Up to 20 cm of recent snow has buried a variety of old snow surfaces. These consist of heavily wind scoured areas and old wind slabs, surface hoar in sheltered areas, and widespread faceted (sugary) old snow. Recent moderate winds from a variety of directions has redistributed some of this new snow on leeward slopes, forming reactive wind slabs. The mid pack appears to be quite variable throughout the region and the structure is dependent on snow depth. 50-80 cm of consolidated snow sits above the mid-December facets. In deeper snowpack areas, the snowpack appears to be well settled and right side up with isolated concerns for the mid-December weak layer. In shallow snowpack areas and lower elevations, the snowpack is heavily faceted and there are concerns for the mid-December weak facet layer as well as weak basal facets. If a persistent slab is triggered from thinner snowpack areas it may release on the basal facets (full depth avalanche). At this point it seems like a low probability, high consequence scenario. However; once the snowpack starts to see a big change, like warming then the likelihood of triggering may increase.

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.