Avalanche Forecast

Issued: Mar 17th, 2022 4:00PM

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

Avalanche Canada rbuhler, Avalanche Canada

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Reactive new wind slabs are expected to be the primary concern for Friday. However, if the sun makes an appearance during the afternoon, solar-triggered loose avalanches are also possible. 

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Unsettled conditions are expected for Friday before a weak storm system arrives early Saturday morning bringing light snowfall through most of Saturday. 

Thursday night: Mainly cloudy with flurries, light to moderate SW wind, freezing level around 1000 m. 

Friday: Mainly cloudy with a chance of both flurries and sunny breaks, light to moderate SW wind, freezing level reaching around 1400 m. 

Saturday: Snowfall 5-15 cm, moderate S-SW wind, freezing level around 1300 m. 

Sunday: A mix of sun and cloud, light W wind, freezing level around 1200 m. 

Avalanche Summary

On Wednesday, several natural storm slabs up to size 1.5 were observed in the Coquihalla area which occurred in the prior 24 hours. A small natural glide slab was also reported. In the north of the region, numerous natural size 1-1.5 wind slabs were reported on north and east aspects in the alpine. 

On Tuesday, a natural size 2 storm slab was reported in the Coquihalla area as well as a natural size 1.5 wind slab on northeast aspect at 1900 m. In the north of the region, several human-triggered storm/wind slabs were reported up to size 2. These were on a variety of aspects between 1850 and 2400 m elevation. Slab thickness varied from 20-60 cm and a few were reported to be sliding on the underlying crust which was buried around March 12. 

Snowpack Summary

Prior to Thursday's snowfall, 20-40 cm of older storm snow which started accumulating on the weekend overlies a melt-freeze crust on sun-exposed aspects and wind-affected or well-settled old snow on shaded aspects. Recent observations suggest this snow is relatively well bonded to the underlying surface. Recent and ongoing wind has redistributed the storm snow into reactive wind slabs in exposed terrain. 

In the north of the region, a crust/facet interface from February sits 30-60 cm deep and had been most problematic on north to northeast aspects around 1900-2100 m. This layer produced a number of avalanche in early March but is now considered dormant and no longer seems to be creating a problem in the region.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.

Problems

Wind Slabs

An icon showing Wind Slabs

Recent southwest wind has formed wind slabs in exposed terrain at higher elevations. These slabs are expected to remain reactive to human triggering on Friday. 

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet

Solar-triggered loose avalanches are possible during the afternoon if the sun is shining brightly. 

Aspects: South East, South, South West, West.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Mar 18th, 2022 4:00PM

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