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Avalanche Forecast

Archived

Apr 19th, 2019–Apr 20th, 2019

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

Fresh storm slabs at upper elevations will likely be reactive to human triggers; especially in lee features below ridgetops.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

FRIDAY NIGHT: Clearing / Light, northwesterly winds / Alpine low -1 C / Freezing level 1800 m.

SATURDAY: Sunny / Light, northwesterly winds / Alpine high 0 C / Freezing level 2000 m.

SUNDAY: Sunny / Light, southwesterly winds / Alpine high 3 C / Freezing level 2400 m.

MONDAY: Sunny / Light, southwesterly winds / Alpine high 4 C / Freezing level 2500 m.

Avalanche Summary

Numerous small (size 1) skier triggered loose wet avalanches were reported on Thursday.

On Tuesday, two naturally triggered size 1.5 storm slab avalanches 25 cm deep were reported on northwest aspects 2200-2400 m.

Several recent natural slab avalanches up to size 2 have been reported on north and east aspects in the alpine. The suspected weak layer was either a crust or small surface hoar that was down 25-50 cm.

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 15-20 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.