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Avalanche Forecast

Archived

Mar 13th, 2014–Mar 14th, 2014

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

Regions

Purcells.

The hazard may be higher than expected if temperatures go higher in the afternoon than forecast. For more insight into the current tricky conditions, see the latest:Forecasters Blog.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Synopsis: The ridge of high pressure begins to break down with incoming Pacific frontal systems.  All parts of the region should receive precipitation in the next few days.Tonight: Cloudy, with a trace of precipitation in the forecast,  freezing level at valley bottom. Ridge top winds light from the south west, occasionally gusting to strong.Friday: Cloudy with flurries, trace of precipitation, freezing level around 1700 metres, winds from the west- light ,gusting moderate to strong.Saturday: Cloudy with flurries,  5 to 10 cm of precipitation, freezing level around 1600 metres, ridge top winds light to moderate from the south west.Sunday:  Cloudy, 10 to15 cm of precipitation in the forecast, freezing level around 1600 metres.

Avalanche Summary

Large natural avalanches are still being reported throughout the forecast area. Explosives control has also produced some quite large results in some cases with wide propagations running full path over 1600 vertical metres. Recently size 2.5 avalanche was triggered by snowboarders at 2600 metres on a south east aspect. Neighboring forecast regions have reported large avalanches initiating in the new storm snow, then stepping down to deeper layers, some running full path to the ground. Cornice failures triggering large avalanches have been reported.

Snowpack Summary

The recent snowfall has now developed into a dense slab. In some deeper snowpack areas 80 to 100cm of storm slab overlies a weak surface hoar and facet layer that has been preserved in sheltered areas. A buried sun crust exists on solar aspects and and touchy wind slabs have formed at tree line and above. On lee slopes these accumulations have been pushed into much deeper deposits by moderate to strong southwest winds. Warming has added cohesion to the slab and wider propagations are now being reported. With rising temps and solar radiation, moist snow surfaces have been reported into the alpine. Wet avalanches on solar aspects have also been reported. There is ongoing concern for a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 60 and 160cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. In parts of the forecast area, large destructive avalanches are still a very real concern with ongoing reports of natural avalanches running full path. Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.