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Avalanche Forecast

Archived

Jan 13th, 2014–Jan 14th, 2014

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

Regions

Sea To Sky.

We're dealing with an unusual snowpack right now on the Sea to Sky. Check out the recent Forecasters Blog post for a more detailed discussion

Confidence

Good

Weather Forecast

Synopsis: A clearing trend as a warm ridge builds over the region causing  rising freezing levels.  There is the possibility for some light precipitation Tuesday night as a cold front slides down the coast although this front will not displace the warm air.Tonight and Tuesday: Cloudy with sunny periods / Winds moderate to strong westerly / Freezing continue to rise as high as 2500m.Wednesday: Clearing with sunny periods / Winds moderate to strong westerly / Freezing level 2500m.Thursday: Sunny / Winds light westerly / Freezing levels 3000m

Avalanche Summary

We've receive reports confirming a wide spread natural avalanche cycle that ran through the weekends storm. Importantly several large avalanches were observed to have released at or close to the ground, confirming a deep persistent slab problem exists in the region.

Snowpack Summary

Last weekends storm clobbered the region with up to 100 cm of snow. This fell on a couple of layers of surface hoar found in sheltered terrain at and below treeline. The unrelenting southwest to south winds have formed large and touchy wind slabs in the alpine and at treeline.Although on the surface things are starting to look more a little more normal than they have it is important to remember that this latest snow fell on a fundamentally thin and weak snowpack. The cold temperatures of early December left persistent weak faceted crystals that seem to be variably reactive. At higher elevations where the snowpack was deeper, the facets likely co-exist with a crust. At lower elevations or in thin, rocky alpine features more widespread facets exist down near the ground. This makes for a low probability high consequence avalanche scenario that is more commonly associated in the interior of the province. The "wait 48 hours and you're good" Coastal mantra does not apply as these conditions are likely to persist for some time.In glaciated terrain open and poorly bridged crevasses are everywhere although now they are hiding under a meter of unsupportive storm snow.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.