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Avalanche Forecast

Archived

Apr 15th, 2017–Apr 16th, 2017

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

Regions

Lizard-Flathead.

Expect the avalanche danger to increase as the sun comes out and temperature rises through the day.

Confidence

Low - Due to the number of field observations

Weather Forecast

SUNDAY: Mix of sun and cloud / Light southeast wind / Alpine temperature 2 / Freezing level 1700mMONDAY: Cloudy with sunny breaks / Light to moderate south wind / Alpine temperature 5 / Freezing level 2100mTUESDAY: Isolated flurries / Light to moderate south wind / Alpine temperature 4 / Freezing level 2000m

Avalanche Summary

Reports on Thursday indicate numerous skier controlled and natural loose wet avalanches to size 1.5 on all aspects up to 2000m. Additionally a few explosive controlled moist storm slab avalanches were reported to size 2, 20-30cm deep on north and east aspects above 2000m. Exposure to large overhanging cornices remains a significant concern. As the sun comes out over the weekend expect to see cornices weaken and loose snow avalanches run from steep sun exposed slopes during the warmest parts of the day.

Snowpack Summary

Up to 20cm of moist new snow fell at upper elevations Wednesday night. Thursday during the day the precipitation fell as rain up to 2000m making the snow surface moist or wet. Subsequent overnight cooling has created thin surface crusts up to 2100m. All this adds to moist new snow from the previous weekend and sits on a well developed crust layer. The snowpack is generally well settled and continues to transition into a spring melt/freeze regime. Below 1300m the snowpack may be moist or wet through its entire thickness. In the alpine cornices continue to grow large and ever more overhanging.

Problems

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.