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Archived

Avalanche Forecast

May 8th, 2019–May 9th, 2019
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Jasper.

Soaring freezing levels and hot sun will stress a relatively cool, wintery snowpack.  The sound of natural avalanches will echo around the hills this weekend - steer clear of avalanche terrain Friday onwards. Start very early if traveling on snow.

Weather Forecast

Freezing level soaring, with valley bottom highs forecast in the 20's.  Generally scattered cloud, warm overnight temperatures.

Thursday: Mainly sunny, Treeline low -1, high 6 °C, Light NW winds, Freezing level 3100 metres.

Friday: Treeline low 2.5, High 7. freezing level 3000m.

Saturday: Treeline Low 5, High 1, freezing level 3500m1

Snowpack Summary

Surface layers becoming wet daily, as the snowpack is forced to transition rapidly from Winter to Spring.  Snow from frequent small Spring storms has settled quickly, but overlies crusts and facets in the upper snowpack. The crusts are thick on solar aspects.  The snowpack remains faceted on shady aspects, and weak in shallow areas.

Avalanche Summary

On Wednesday, numerous small (size 1-1.5) loose wet avalanches were observed on N and E aspects near Jasper townsite.  On Sunday, a large (size 2.5) natural slab avalanche was observed at 2400m on a NE aspect of Pyramid Mountain. 

Confidence

Due to the number of field observations

Avalanche Problems

Loose Wet

Springs' increasing influence is encouraging the upper snowpack to shed recent snowfall, in loose snow avalanches. Steer away from avalanche terrain as the upper snowpack becomes wet, and you are sinking in to bootop or deeper.

  • Travel early before the heat of the day melts surface crusts, and avoid big slopes in the afternoon.
  • If triggered loose wet sluffs may step down to deeper layers resulting in larger avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

Weak mid-pack facets and upper-snowpack crusts will become more reactive, especially on shaded, wind-sheltered slopes. This may morph into a Wet Slab problem on solar aspects, as water accumulates above strong crusts.

  • If off-trail travel is deep and punchy, avoid all avalanche terrain, including runouts.
  • Minimize exposure to big slopes, especially during the heat of the day.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1.5 - 3

Cornices

Occasional cornice falls are expected, increasing into the weekend. some of these may trigger large slab avalanches, running well down into lower elevations. 

  • Minimize exposure to overhead hazard from cornices.
  • Stay well to the windward side of corniced ridges.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3.5