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Avalanche Forecast

Archived

Feb 1st, 2021–Feb 2nd, 2021

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Rockies.

A bit of new snow forecast Monday night in the south and central part of the region will combine with moderate wind to create fresh wind slabs in exposed terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

MONDAY Night: Flurries with 5-10 cm of snow, moderate southwest wind, treeline temperatures around -10 C.

TUESDAY: Cloudy with scattered flurries with 3-5 cm, moderate southwest wind, treeline temperatures around -12 C.

WEDNESDAY: Mainly cloudy, moderate west wind, treeline temperatures around -10 C.

THURSDAY: Flurries, accumulation 5-10 cm, moderate northwest wind, treeline temperature around -8.

Avalanche Summary

No avalanches have been reported recently. That being said, some notable shooting cracks and whumpfs were reported around Pine Pass last Thursday. They were both linked to buried surface hoar layers, one 30 cm deep underneath a fresh wind slab (here) and the other 65 cm deep underneath old snow (here). 

Snowpack Summary

Open terrain is likely being impacted by moderate wind, with wind slabs forming on lee terrain features. Sheltered areas have 10-20 cm of soft faceted snow. Underneath the soft snow and new wind slabs, you will likely find a hard melt-freeze crust up to roughly 1600 m, perhaps weak and feathery surface hoar crystals, and otherwise wind packed snow. Wind slabs developing above surface hoar could be particularly reactive.

There is a spotty weak layer of surface hoar 30 to 65 cm deep in sheltered treeline terrain. This layer has not produced any avalanches to date, but our field team reported some large whumpfs on this layer at Pine Pass on Thursday.

There are presently no deeper concerns in the snowpack.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

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.