South Coast Inland Avalanche Forecast

Issued: Mar 1st, 2021 4:00PM

Tue Mar 2nd Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Low
Wed Mar 3rd 2 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Considerable
Thu Mar 4th 3 Day Outlook
Alpine Considerable Treeline Considerable Below Treeline Considerable

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Light snowfall and strong southwesterly wind will keep wind slabs fresh Tuesday. Older wind slabs exist on a variety of aspects and may remain reactive where they sit over facets.

Warm temperatures ahead for the south of the region.

Summary

Confidence

Moderate - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

Monday night: Flurries up to 5 cm. Strong southwesterly wind above 2000 m. Freezing level dropping to 500 m.

Tuesday: Flurries up to 5 cm. Wind southwesterly light below 2000 m, moderate 2000-2500 m, strong above. Freezing level 1100 m.

Wednesday: Mix of sun and cloud. Light to moderate southerly winds. Freezing level rising to 1500 m in the north and 2000 m in the south.

Thursday: Mix of sun and cloud. Moderate to strong southerly winds. Freezing level rising to 2000 m in the north and 2200 m in the south.

Avalanche Summary

On Sunday, a size 1.5 skier accidental was reported on a northwest aspect in the alpine near Duffey Lake. The slab is thought to have failed on a thin layer of underlying facets over the firm bed surface of old, previously wind-stiffened snow. 

The Coquihalla area saw heavy skier traffic over the weekend reporting mainly good ski quality in the trees, with visible wind transport at higher elevations. A skier triggered wind slab on a northeast aspect around treeline is described in this MIN.

Snowpack Summary

At upper elevations, wind transport and fresh wind slab formation will likely continue with a modest supply of new snow. 

In the north of the region, 15-30 cm of snow sits over a widespread layer of facets and isolated crusts. The interface appears largely unreactive except for areas where the facets thinly overlie hard old surfaces. In the Coquihalla area, 60-80 cm appears to be bonding well to the underlying surface which may also include crusts on steep solar aspects and below 1500 m.

A persistent weak layer composed of a crust, facets or surface hoar depending on elevation/aspect is now down 70-120 cm. This layer, buried in late January, continues to be noted in snowpack tests with mixed results. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow/ wind and/or a rapid rise in temperature can awaken these deeper weak layers.

The lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible-Likely

Expected Size

1 - 2

Light snowfall and strong southwest wind are likely forming fresh, thin wind slabs in lee features at upper elevations. Older wind slabs exist on a variety of aspects and may remain reactive where they sit over a thin layer of facets on a hard bed surface.

Cornices are likely growing as well. Fresh, unsupported tabs breaking off can be dangerous on their own, they can also act as triggers on slopes below.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Mar 2nd, 2021 4:00PM

Forecast Trend

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