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Avalanche Forecast

Archived

Apr 13th, 2019–Apr 14th, 2019

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

Regions

Purcells.

Lingering wind slabs may still be reactive to human triggers in isolated locations, such as steep, north facing slopes below alpine ridgetops.

Confidence

High -

Weather Forecast

SATURDAY NIGHT: Cloudy with flurries; 0-3 cm. / Moderate, southwesterly winds / Alpine low -5 C / Freezing level 1200 m.SUNDAY: Mix of sun and cloud with isolated flurries; 0-3 cm. / Light, westerly winds / Alpine high -2 C / Freezing level 1600 m.MONDAY: Mix of sun and cloud / Light, southwesterly winds / Alpine high -2 C / Freezing level 1600 m.TUESDAY: Mostly sunny / Light, westerly winds / Alpine high 0 C / Freezing level 1800 m.

Avalanche Summary

On Friday, explosive cornice control work dropped a large cornice on a rocky slope which triggered a size 2.5 slab avalanche 50 cm deep on a northeast aspect.On Tuesday, skiers were able to trigger slabs up to size 1.5 in steep, gully features as low as 2200m. Explosives produced avalanches to size 2 and a helicopter remotely triggered a size 1.5 avalanche from 200 m away. They initiated in steep, alpine terrain above 2400 m, mostly on northerly aspects.

Snowpack Summary

Currently, the snowpack structure changes dramatically with elevation and aspect. 5-25 cm. of recent storm snow (amounts tapering with elevation) is sitting on a melt/freeze crust, except for north facing terrain above 2100 m. where the old snow surface remained dry and small surface hoar (weak, feathery crystals) may be present in isolated locations. This recent snow has been affected by the sun and re-distributed by southwesterly winds, forming wind slabs on lee features below ridgetops.Weak facets (sugary grains) remain at the bottom of the snowpack in the alpine creating a low likelihood, high consequence scenario that would likely require a large trigger to initiate an avalanche. Steep, rocky areas with a shallow or highly variable snowpack are the most likely places to trigger a very large avalanche on this layer.Below roughly 1900 m, the snowpack is moist and is melting rapidly at lower elevations. Check out this useful link for managing avalanche hazard during spring conditions HERE.

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.