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Avalanche Forecast

Mar 15th, 2020–Mar 16th, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Expect an upward swing in temperatures as the freezing level rises on Monday. This shift in temperature may result in a rise in the likelihood of triggering persistent slab avalanches. Be especially cautious underneath steep sun exposed slopes and around rock outcrops.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

SUNDAY NIGHT: Mainly clear, light northeast wind, alpine temperature -8 C.

MONDAY: Clear skies, light northwest wind, alpine temperature -1 C, freezing level 1800 m.

TUESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -2 C, freezing level 1700 m.

WEDNESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -4 C, freezing level 1500 m.

Avalanche Summary

There were reports of a few natural wind slab avalanches on the weekend size 1.5 to 2.5 on north and southeast aspects in the alpine. 

Snowpack Summary

Recent moderate to strong northeast and east wind has redistributed the snow and formed wind slabs at all elevations. New snow from last week may sit on a weak surface hoar layer and a sun crust on steep solar aspects. 

A weak layer of surface hoar buried February 22 may be found 50-100 cm deep. It may sit over a crust on solar aspects. This persistent weak layer will likely remain a problem until there is a substantial change in the snowpack. Read more about surface hoar on our forecaster blog.

Deeply buried facets lurk near the bottom of the snowpack. This layer has been responsible for sporadic deep persistent slab avalanches, usually triggered from shallow, rocky start zones.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Avalanche Problems

Wind Slabs

Moderate to strong northeast and east wind formed wind slabs at all elevations which might be reactive to human triggers. 

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

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer of surface hoar sits 50-100 cm deep, within the range for human-triggering. Over the past week, large human-triggered avalanches have released on this layer.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1.5 - 2.5

Deep Persistent Slabs

Weak facetted snow at the near the base of the snowpack continues to be a concern. Treat wind-scoured, rocky, shallow terrain as suspect and avoid big alpine slopes that are threatened by cornices overhead. 

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3.5