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Avalanche Forecast

Archived

Mar 30th, 2022–Mar 31st, 2022

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

Regions

North Rockies.

Cautious route-finding will be important at upper elevations as fresh wind slabs are likely to trigger.

If the sun comes out, wet loose avalanches may occur in steep terrain. Be aware of what is above you, and avoid exposure to steep slopes and cornices baking in the sun

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with flurries. Freezing level dropping to 500 m. 20-50km/h westerly winds at ridge top.

THURSDAY: Mainly cloudy with scattered flurries, light accumulation. Freezing level rising to 1300 m. 15-40 km/h westerly winds. 

FRIDAY: Cloudy with isolated flurries. Light southwesterly winds increase to 30-50 km/h in the afternoon. Freezing level rising to 1400 m.

SATURDAY: Scattered cloud cover. 15-30 km/h southwesterly winds. Freezing level rising to 1500 m.

Avalanche Summary

Several small (size 1) wet loose avalanches were observed in the Kakwa on Tuesday out of steep terrain as a result of warm temperatures and strong solar radiation.

On Monday, a size 1.5 skier-triggered wind slab occurred on south aspect at treeline. This wind slab failed on a slick crust below the new snow. 

Snowpack Summary

5-15 cm of new snow overlies 20 cm of denser snow that tapers rapidly with elevation. Westerly winds have formed small pockets of windslab in the alpine and exposed treeline. A crust or moist snow can be found below the new snow on all aspects as high as 2000 m and to mountain top on solar aspects. Below the crust, the top 10-30 cm of the snowpack is moist.

There are no deeper concerns at this time.

Terrain and Travel

  • Cornices become weak with daytime heating or solar exposure.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs may be poorly bonded to the underlying crust.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.