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Avalanche Forecast

Archived

Apr 21st, 2019–Apr 22nd, 2019

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

Regions

Northwest Coastal.

Forecast precipitation and wind will drive the avalanche danger to High in the alpine on Monday. Due to a very limited number of information sources at this time of year, this report is based off of weather forecast information only.

Confidence

Low - Due to the number of field observations

Weather Forecast

SUNDAY Night: Snow at upper elevations, accumulation 10-20 cm / moderate to strong south wind / alpine temperature -2 C, freezing level 1000 m

MONDAY: Snow at upper elevations, accumulation 10-15 cm / moderate to strong southwest wind / alpine high temperature 0 C / freezing level 1200 m

TUESDAY: Mainly cloudy with scattered flurries and sunny breaks / moderate southwest wind / alpine high temperature -4 C / freezing level 800 m

WEDNESDAY: Cloudy with sunny periods / light to moderate west wind / alpine high temperature -3 / freezing level 900 m

Avalanche Summary

No new avalanches have been reported in the region. Expect to see an increase in storm slab activity with snowfall and wind at upper elevations along with increased wet loose avalanche activity at lower elevations associated with rainfall there. Please submit your observations to the Mountain Information Network.

Snowpack Summary

Expect to see an additional 10-20 cm of new snow in the alpine on Monday morning to add to the 20-40 cm of snow that fell through the last week at upper elevations. More precipitation will accumulate throughout the day on Monday. Moderate to strong southwest winds are expected to have formed reactive wind slabs. This new snow sits on a melt freeze crust except for high elevation north aspects. It is likely that the most recent precipitation is falling as rain 1000 m and below.

A crust that formed in early April is down 30 to 100 cm on high elevation north facing slopes. Surface hoar and facets were previously observed on this crust and it recently produced sudden results in snowpack tests. At lower elevations, ongoing warm weather has been promoting isothermal snowpack conditions and melting the snowpack away.

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.