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Avalanche Forecast

Archived

Apr 8th, 2022–Apr 9th, 2022

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

Regions

North Rockies.

Strong West winds combined with an additional 10-20 cm of new snow may build fresh and reactive wind slabs. 

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

A cool and unstable weather pattern will exist through the weekend.

Friday Night: New snow 5-10 cm. Moderate to strong West winds at ridgetop and freezing levels near valley bottom. 

Saturday/ Sunday: Cloudy possible sunny periods with new snow 5-10 cm. Moderate ridgetop wind from the northeast. Freezing levels 1000 m. Alpine temperatures near -10 C.

Monday: Mix of sun and cloud. Freezing level near 700 m and alpine temperatures -15 C. Ridgetop winds light from the West.

Avalanche Summary

On Thursday, in the Renshaw area, the field team reported a natural cornice fall from a North-facing alpine slope. This cornice triggered a size 2 slab avalanche from the slope below. 

Snowpack Summary

A new surface crust may exist to 2000 m and higher on southerly aspects and 10 cm of new snow may be found in the alpine. 

Over the past week, up to 50 cm of storm snow blanketed upper elevations. Light to moderate wind may have redistributed the storm snow in exposed high elevation terrain forming pockets of wind slab and large cornices. 

50-70 cm of consolidated snow sits on the thick melt-freeze crust from late March. There has been no recent avalanche activity reported on this layer.

Terrain and Travel

  • 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.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.