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Avalanche Forecast

Archived

Apr 20th, 2019–Apr 21st, 2019

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

Regions

Jasper.

Up to 30cm of recent heavy snow with winds has activated the problems with continuing natural activity. Give the new snow a couple of days to settle and bond.

Weather Forecast

The next couple of days will be generally sun and cloud, no new snow except for maybe a little on Monday and Tuesday, and rising incrementally freezing levels. A wind event may arrive Monday evening with 70km/hr winds.

Snowpack Summary

Moderate winds, mild temperatures and 30cm of new heavy snow Thursday night created widespread slabs in the alpine and into tree line. It rained at lower elevations making isothermal conditions where enough snow exists. A persistent facet weak layer down 40-70cm exists in some locations.

Avalanche Summary

Saturday's field patrol observed loose wet up to size 2, persistent slabs to size 3 on mainly NE aspects in alpine, and also thin windslabs size 2-2.5 E aspects. Yesterday there was a natural cycle with the recent 30cm storm. Friday's avalanche control on Highway 93 produced several wind slab avalanches up to size 2 and some stepped down.

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.