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Avalanche Forecast

Archived

Feb 16th, 2017–Feb 17th, 2017

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

Little Yoho.

Potential for large avalanches persist. Conservative route choices remain the theme of the day. Iceclimbers should pay attention to freezing levels and adjust there route choices accordingly.

Weather Forecast

Friday will be mainly cloudy with some isolated flurries. Freezing levels will be around 1300m and the winds will be moderate from the west. There will be a continued cooling trend for Saturday.

Snowpack Summary

10-20 cm of fresh snow (at treeline) and up to 50 cm of storm snow in the past week have formed a cohesive slab overtop of a series of weak layers. Test results show sudden shear failures on these layers. Moderate SW winds have created fresh wind slabs on lee aspects at treeline and above. Below 1800 m the snowpack is moist from rain event on Thur.

Avalanche Summary

Warm temps and rain below 1800m in Field on Thursday triggered a loose wet avalanche cycle at lower elevations. Avalanches up to size two were observed running over several of the ice climbs on Mt Dennis. A Class 3 avalanche occurred in past few days on Emerald Lake slide path.

Confidence

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.

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.

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.