Avalanche Forecast

Archived

Apr 21st, 2014–Apr 22nd, 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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Below Threshold.

Treeline

Below Threshold.

Below Treeline

Below Threshold.

Regions

Kootenay Boundary.

Resist the urge to rely on danger ratings alone. Conditions change rapidly at this time of year and you need to stay tuned in to local conditions.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Tuesday: Cloudy with showers or flurries 10-20 mm or cm depending on elevation. The freezing level is around 2000 m lowering to 1500 m in the evening. Ridge winds are light to moderate from the S-SE. Wednesday: Cloudy with sunny breaks and scattered flurries. The freezing level is around 1500 m and ridge winds are moderate from the SW. Thursday: Mainly cloudy with showers or flurries developing. The freezing level is around 2000 m and winds are light but gusty from the south.

Avalanche Summary

Expect loose wet avalanches in steep terrain if it is raining or during sunny periods, especially if the sun or rain is affecting fresh snow. New storm of wind slabs may develop in higher terrain if we see significant new snow accumulation. Make conservative terrain choices if you see 30 cm of new snow or more in 24-48 hours or significant loading from strong winds. There is still potential for deep persistent slabs to wake up. This is most likely during periods of heavy rain or warm temperatures and strong solar radiation. Your best bet is to pack it in when the snow surface is becoming really wet and mushy.

Snowpack Summary

This is a broad general summary of conditions in the region. This summary is based on very limited field data and should be supplemented with local observations to help assess avalanche danger. Over the past week or so we have seen moderate amounts of moist new snow mixed with showers or periods of rain below 1600-1800 m. Westerly winds have likely formed pockets of wind slab at higher elevations in lee of ridges and terrain features. The upper snowpack generally consists of layers of moist or wet snow mixed with several well bonded crusts. Most areas are likely below threshold for avalanches below 1300-1500 m depending on aspect. The late January/early February persistent weak layer is deeply buried but could still wake up during periods of heavy precipitation (especially rain) or significant warming and solar radiation. Be particularly wary of this on large open alpine slopes. Cornices are large in some areas and should be given a wide berth.

Problems

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.