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Archived

Avalanche Forecast

Dec 29th, 2017–Dec 30th, 2017
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Continued slow accumulation of new snow Friday night into Saturday just before a more stable and clearing weather pattern sets in for the rest weekend.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

SATURDAY: 5-10cm overnight Friday into Saturday then cloudy with isolated flurries / Light to moderate northwest wind / Alpine temperature -12 SUNDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -8 MONDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -5

Avalanche Summary

Recent reports continue to show both natural and human triggered loose dry avalanches in steep terrain to size 1 in areas that have not been affected by wind. Additionally isolated wind slab avalanches have been reported in the alpine to size 1. Expect continued potential for triggering loose dry avalanches in steep terrain and consider the potential to trigger persistent slabs where last week's storm snow has settled into a cohesive slab.

Snowpack Summary

10-20cm low density new snow has accumulated and buried a recently formed layer of weak feathery surface hoar and/or sugary facets. Another layer buried mid-December that consists of surface hoar, sun crust and/or sugary facets is down approximately 30-50cm. The bond at this old snow interface is of critical importance where the overlying storm snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, such as sheltered areas at and below treeline and any area where the surface hoar may have formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this layer but suggest that it may be most reactive on northerly aspects. A rain crust that formed in late November is now buried 60-100cm deep. Recent reports show this layer to be unreactive at this time.

Avalanche Problems

Wind Slabs

Recent northwest, west and southwest winds have created wind slabs in the lee of terrain features.
Be cautious as you transition into wind affected terrain.Travel on ridges and/or ribs to avoid wind loaded slopes below

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

A weak layer of surface hoar buried 30-50 cm deep may be reactive where the overlying snow has settled into a cohesive slab.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Approach steep open slopes cautiously at and below treeline where buried surface hoar may exist.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 2