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Archived

Avalanche Forecast

Mar 21st, 2020–Mar 22nd, 2020
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

Fresh storm slabs will build as 15-25 cm of new snow falls through the day Sunday. Human triggering will be especially likely where new snow has been wind-loaded into lee terrain features and where it sits over a crust.

Confidence

High -

Weather Forecast

Saturday night: Clear. Moderate northwest wind. Freezing level 1000 m.

Sunday: 15-25 cm new snow. Light to moderate southwest wind. Freezing level 600 m.

Monday: Scattered flurries bringing up to 5 cm. Light northeast wind. Freezing level 1000 m.

Tuesday: Flurries. Light north wind. Freezing level 1000 m.

Avalanche Summary

Natural loose wet avalanche activity has been observed on sun-exposed slopes during the heat of the day over the last few warm days. A few cornices were also triggered by the warming. Glide slab activity has also 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

15-25 cm of new snow is falling over extensively wind-affected surfaces and over melt-freeze crusts on solar aspects and low elevations.

A layer of surface hoar crystals is buried around 40 to 80 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

  • Watch for fresh storm slabs building throughout the day.
  • 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.

Avalanche Problems

Storm Slabs

15-25 cm of new snow is forming storm slabs over wind-affected surfaces, crusts and possibly isolated patches of surface hoar. Expect human triggered avalanches at this interface, especially on steep solar aspects and lee terrain features where moderate winds have loaded new snow into deep pockets.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer of surface hoar crystals is buried around 30 to 60 cm and has been reactive to both human and natural triggers. This weak layer is most problematic in sheltered terrain at treeline elevations, where the surface hoar remains preserved.

Aspects: North, North East, East, West, North West.

Elevations: Treeline, Below Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1.5 - 2.5