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Archived

Avalanche Forecast

Apr 1st, 2021–Apr 2nd, 2021
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
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

Regions: Northwest Coastal.

Additional snow and wind will continue to form reactive storm slabs on Friday. Use small slopes with low consequence to test the bond of the new snow. Be especially cautious in wind affected terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

  

THURSDAY NIGHT: Snow; 5-10 cm. / Strong, southwest ridgetop wind / alpine low temperature -7 / Freezing level valley bottom.

FRIDAY: Snow/rain; 10-20 mm, and another 5-15 cm. overnight / Strong, southwest ridgetop wind / alpine high temperature -1 / Freezing level 800 m.

SATURDAY: Flurries in AM and clearing in PM; 0-3 mm. / Light, southwest ridgetop wind / alpine high temperature -1 / Freezing level 800 m.

SUNDAY: Mix of sun and cloud / Moderate, northwest ridgetop wind / alpine high temperature -1 / Freezing level 800 m.

Avalanche Summary

On Wednesday, naturally triggered glide slab avalanches were reported up to size 3. Glide cracks releasing as full depth glide slab avalanches are extremely difficult to predict. Best practice is to avoid slopes with glide cracks.

Snowpack Summary

Storm snow amounts will continue to accumulate overnight Thursday and throughout the day on Friday, forming reactive storm slabs. 

The recent snow adds to the 30-60 cm. that fell at upper elevations last weekend. Much of the recent precipitation fell as rain at lower elevations and the snow surface below treeline is a melt-freeze crust in many areas.  

At higher elevations, the new snow has added significant load to a couple of deeply buried weak layers. The first persistent weak layer was buried in mid-March and is around 100-180 cm deep. It consists of surface hoar on sheltered northerly aspects around treeline and down between 150 to 250 cm is another layer of surface hoar and facets, buried in mid-February. At this time, these layers linger in the snowpack but haven't recently been a reactive avalanche problem. 

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

Terrain and Travel

  • Watch for fresh storm slabs building throughout the day.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Start with conservative lines and watch for clues of instability.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Avalanche Problems

Storm Slabs

Reactive storm slabs are expected at upper elevations, especially in wind-loaded areas where fresh wind slabs may be the primary concern. 

Loose-dry avalanches may occur from steeper terrain features. 

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1.5 - 2.5

Cornices

Cornices are large and looming along many ridgelines, and have likely grown with the recent snow and wind. They require a large berth from above and below. 

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1.5 - 2.5