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Avalanche Forecast

Archived

Mar 22nd, 2020–Mar 23rd, 2020

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
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

Northwest Coastal.

In areas where more than 20 cm of new snow has accumulated, watch for small loose dry avalanches and isolated pockets of thin but potentially reactive storm slab. An underlying crust makes a great bed surface and avalanches may run surprisingly far.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Sunday night: Up to 5 cm new snow. Light northeast to southeast wind. Freezing level 600 m.

Monday: Flurries. Light northeast wind. Freezing level 900 m.

Tuesday: Up to 5 cm new snow then clearing. Moderate northeast wind. Freezing level 700 m.

Wednesday: Clear. Moderate northwest wind. Freezing level 1000 m.

Avalanche Summary

Loose wet avalanches were observed on solar aspects during the warm, sunny week. A few cornice failures were also observed but did not trigger slabs. Glide slab activity has been reported recently out of steep terrain where snow sits over smooth surfaces. 

If you decide to travel in the backcountry, consider sharing your observations with us and fellow recreationists via the Mountain Information Network (MIN) to supplement our data stream as operators are shutting down. Even just a photo of what the day looked like would be helpful.

Snowpack Summary

Up to 25 cm of new snow sits over melt-freeze crusts on solar aspects, and extensively wind affected surfaces in exposed terrain that did not see the sun. 

A layer of surface hoar crystals is buried around 30-60 cm in sheltered areas at and below treeline. See this MIN from the Shames area that shows this layer when it was on the surface, prior to burial on March 9.

An early-season layer of faceted grains and a melt-freeze crust may linger at the base of the snowpack. A large load, such as a cornice fall, has the potential of triggering it.

Terrain and Travel

  • Closely monitor how the new snow is bonding to the crust.
  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.