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Avalanche Forecast

Archived

Jan 31st, 2022–Feb 1st, 2022

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

Lizard-Flathead.

The recent storm snow is expected to remain touchy on Tuesday, especially in wind loaded terrain and on steep slopes where it overlies surface hoar or a crust. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Unsettled conditions are expected on Tuesday as Arctic air shifts southward. 

Monday Night: Partly cloudy, light variable wind, treeline temperature dropping to around -12 C°.

Tuesday: Mainly cloudy with snow flurries up to 5 cm, light to moderate wind shifting to the NE, treeline high around -10 C°.

Wednesday: A mix of sun and cloud, light variable wind, treeline high around -15 C°.

Thursday: A mix of sun and cloud, light to moderate variable wind, treeline high around -8 C°.

Avalanche Summary

An early report from Monday shows explosives triggering numerous size 2 storm slabs which were releasing down 20-30 cm and propagating widely. On Sunday, a natural size 1 cornice release was reported failing overnight during strong winds. 

Snowpack Summary

Up to 25 cm of new snow has buried a highly variable snow surface which consists of wind affected surfaces in exposed high elevation terrain, a melt freeze crust at lower elevations and on solar aspects extending into the alpine, and/or widespread surface hoar in sheltered areas which is typically 10-20 mm but as big as 30 mm in places. 

The widespread January 18 rain crust is now down around 40-50 cm but has not been creating an avalanche problem recently. The midpack is strong and well-consolidated above the early December facet/crust layer which is now down 100-200 cm. This layer has been dormant recently and is not currently a concern for the region but could still be a problem in the future. See the most recent forecaster blog for more details on this layer. 

Terrain and Travel

  • Be especially cautious as you transition into wind affected terrain.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

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.