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Avalanche Forecast

Archived

Apr 18th, 2022–Apr 19th, 2022

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

Regions

Sea To Sky.

Touchy storm slabs reactive to human triggers will form at all elevations Monday night. These slabs will be most reactive on lee features at treeline and above.

Expect the danger to be HIGH in localized areas that receive more than 25 cm of new snow Monday night.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system. Forecast snowfall amounts are uncertain.

Weather Forecast

Monday night: Snow; 15-30 cm / Moderate southwest wind / Low of -7 / Freezing level 900 m.

Tuesday: Mix of sun and cloud / Light southwest wind / High of 0 / Freezing level 1200 m.

Wednesday: Sunny, with increasing cloudiness in afternoon. / Moderate southeast wind / High of 3 / Freezing level 1700 m.

Thursday: Cloudy with isolated flurries; 3-10 cm / Light southwest wind / High of 2 / Freezing level 1500 m.

Avalanche Summary

Human triggered avalanche activity is expected to increase on Tuesday with the 15-30 cm of new snow and moderate southwest winds forecast for Monday night.

Snowpack Summary

Forecast 15-30 cm of new snow Monday night could bring storm totals to 30-50 cm by Tuesday morning. The new snow and strong southwest winds are expected to form large storm slabs that will be reactive to human triggers at all elevations. Expect the storm slabs to be most reactive on lee features at treeline and above.

The recent snow is sitting on a variety of hard snow surfaces, including crusts and wind scoured snow. Below this, there are several crusts in the upper snowpack, but they are unlikely to be a concern in most areas until the next significant warming event.

Terrain and Travel

  • Make conservative terrain choices and avoid overhead hazard.
  • Use small low consequence slopes to test the bond of the new snow.
  • Be careful as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

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.

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.