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Avalanche Forecast

Archived

Mar 31st, 2015–Apr 1st, 2015

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

Regions

Northwest Coastal.

A weak surface hoar layer is creating touchy conditions in some areas. If you have field observations to share, please consider using the Mountain Information Network. Click here for more info.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Generally unsettled conditions are expected for the forecast period.  Wednesday: Up to 5cm of snow / Moderate westerly winds / Freezing level at 1000m  Thursday: Up to 15cm of new snow accumulating between Thursday afternoon and early Friday morning / Strong southwest winds / Freezing level at 1000m  Friday: 2-5cm of snow / Moderate southwest winds / Freezing level at 1000m

Avalanche Summary

In general, observations have been limited in the last few days. That said, in the north of the region several avalanches in the size 1.5-2 range were reported to have been triggered remotely in alpine terrain. The March 25 interface was the culprit in these avalanches. Due to the persistent nature of this interface, avalanche activity on this layer may occur for some time after the stormy weather has ended.

Snowpack Summary

Up to 45cm of new snow has fallen since the weekend. During this period, ridge top winds were generally moderate to strong from the southwest. Dense storm slabs now exist at higher elevations and are expected to be reactive in lee terrain. Below about 1500m, surfaces are reported to be moist or wet.A layer of surface hoar that was buried around March 25 is now around 40-75 cm below the surface. There is some uncertainty regarding the current reactivity and distribution of this layer, although avalanche activity and whumpfs were reported prior to the weekend on northerly aspects in the alpine and at treeline, and touchy conditions are still being reported in the north of the region. I'd maintain a cautious approach to terrain selection as avalanches at this interface could be large and destructive. The mid-pack is generally well-settled and strong. At the base of the snowpack, weak facets may be found, particularly on shallow alpine slopes in the north of the region.

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.

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.