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Avalanche Forecast

Archived

Feb 19th, 2016–Feb 20th, 2016

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

Regions

Little Yoho.

While some improvement with cold temperatures on Sunday this will be mainly at lower elevations that have been affected by recent warm conditions. Continue to use caution Treeline and above until a trend away from frequent avalanche activity is seen.

Weather Forecast

Friday saw a the start of a cooling trend.  Moderate SW winds will shift to West and increase to strong overnight before shifting NW and back to the light range as the last of the precip arrives Saturday morning ahead of an approaching ridge. Saturday afternoon the ridge will build, skies should clear and temperatures drop into Sunday.

Snowpack Summary

Fresh windslab and rapid cornice growth is occurring with 30- 50 cm of recent snow and moderate to strong West winds. A 60-130 cm slab overlies the January 6th weak layer of surface hoar (below 2000m), facets and sun crust. This layer is variable in tests, giving mainly hard results in test pits. The lower snowpack is well settled in the region.

Avalanche Summary

Lots of loose wet activity in the size 1-1.5 range Thursday at treeline and below from warm temperatures and rain in the Little Yoho region. Some larger avalanches ( size 2-2.5) were noted on solar aspects when the sun popped out on Mt. Ogden in the Takakkaw falls area. Warm temps and a bit more rain BTL likely induced a bit more activity today.

Confidence

Problems

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.

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.