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Avalanche Forecast

Archived

Apr 21st, 2019–Apr 22nd, 2019

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

Regions

South Columbia.

Storm slabs at upper elevations may still be reactive to human triggers; especially in lee features below ridgetops.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Clear / Light, southwesterly winds / Alpine low 2 C / Freezing level 2400 m.

MONDAY: Cloudy / Light to moderate, southwesterly winds / Alpine high 3 C / Freezing level 2400 m.

MONDAY NIGHT: Rain/alpine flurries; 3-5 mm. / Moderate, southwesterly winds / Alpine low 2 C / Freezing level 2200 m.

TUESDAY: Rain/ alpine flurries; 3-5 mm. / Light to moderate, southwesterly winds / Alpine high 2 C / Freezing level 2200 m.

WEDNESDAY: Sunny / Light, northwesterly winds / Alpine high 1 C / Freezing level 2000 m.

Avalanche Summary

On Saturday, numerous natural loose wet avalanches up to size 1.5 were reported on all aspects/elevations.

On Friday, Numerous loose wet and slab avalanches to size 2.5 on all aspects in the alpine were reported. Although not in this region, check out this MIN report from Saturday in Glacier National Park HERE.

Snowpack Summary

20-30 mm. of rain has soaked the snowpack at treeline and below. The rain/snow boundary on Friday was around 2200 m. New snow amounts in the alpine will taper rapidly with elevation and likely equate to around 15-25 cm of moist snow at upper elevations adding to the 20-40 cm recent snow which overlies a crust everywhere except high elevation, north facing terrain where preserved surface hoar (weak, feathery crystals) may be present in isolated locations down 30-60 cm. A similar layer buried in early April is down 50-80 cm. Smaller storm slab avalanches may step down to one of these deeper weak layers.

Below treeline, snow is disappearing rapidly.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.