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Avalanche Forecast

Archived

Mar 24th, 2019–Mar 25th, 2019

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

Regions

Lizard-Flathead.

Small loose wet avalanches may gather mass, become much larger, and run farther into low angle terrain than expected.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Cloudy / Light, southwesterly winds / Alpine low -3 C / Freezing level 1200 m.MONDAY: Mix of sun and cloud / Light, southwesterly winds / Alpine high 2 C / Freezing level 2000 m.TUESDAY: Cloudy with flurries (rain below approx. 1400 m.); 3-5 mm. / Moderate to strong, southwesterly winds / Alpine high -1 C / Freezing level 1600 m.WEDNESDAY: Mix of sun and cloud / Light, northeasterly winds / Alpine high 0 C / Freezing level 1500 m.

Avalanche Summary

On Sunday, there was a report near Fernie of a skier triggered, size 2.5 wet slab avalanche that began as a loose wet avalanche and then gathered mass which ran much further than expected through low angle terrain. The below link shows a smaller example of this sort of avalanche.Thursdays reports show continued skier triggered loose wet avalanches reaching size 1.5 on sun-exposed aspects. Check out this video of our South Rockies Field Team HERE.On Wednesday, several avalanches that began as loose wet point releases, then triggered small slabs which entrained or gouged out additional mass, significantly increasing the size and destructive potential of the avalanche.

Snowpack Summary

The prolonged warm spell has transitioned sun exposed slopes in the alpine and all aspects at treeline and below towards becoming isothermal (0 C throughout the snowpack). In these areas that have entered spring conditions, the avalanche hazard will fluctuate greatly depending on the strength of the overnight freeze and how quickly the snowpack is warmed up each day. Check out this guide to managing avalanche hazard during spring conditions HERE.In areas that remained more sheltered from the heat, like northerly aspects in the alpine, there may still be a dry snowpack with a well settled slab sitting on weak facets (sugary snow). Human triggering of persistent slabs on this layer may still be possible; especially in rocky alpine terrain with a shallow or highly variable depth snowpack.

Problems

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.

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.