North Rockies Avalanche Forecast

Issued: Apr 16th, 2021 4:00PM

Sat Apr 17th Current Conditions
Alpine Considerable Treeline Considerable Below Treeline Considerable
Sun Apr 18th 2 Day Outlook
Alpine Considerable Treeline Moderate Below Treeline Moderate
Mon Apr 19th 3 Day Outlook
Alpine Moderate Treeline Moderate Below Treeline Moderate

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Cornices, Loose Wet and Deep Persistent Slabs.

 

Sustained warming continues to increase the likelihood for large cornice failures and wet loose avalanches. Start early and plan to be off large slopes before the heat of the day.

Check out the latest Forecaster's Blog for more information on managing current conditions.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

  

FRIDAY NIGHT: Clear / Light, northwest ridgetop wind / alpine low temperature 0 / Freezing level 2900 m.

SATURDAY: Sunny / Light, northwest ridgetop wind / alpine high temperature 11 / Freezing level 2800 m.

SUNDAY: Mix of sun and cloud / Strong, northeast ridgetop wind / alpine high temperature 0 / Freezing level dropping to 1200 m.

MONDAY: Sunny / Light, northeast ridgetop wind / alpine high temperature 5 / Freezing level 1800 m.

Avalanche Summary

Numerous naturally triggered wet loose avalanches up to size 2 were reported on all aspects on Thursday.

There have been some large deep persistent slab avalanches triggered by warming to the south around Jasper and Banff, but we are uncertain whether this problem will extend into the North Rockies.

Sustained warming can increase the likelihood of large avalanches failing on deeply buried weak layers.This is most likely to occur on steep, rocky alpine slopes with a shallow or thin to thick snowpack. 

Snowpack Summary

Warm temperatures are melting the surface on all but the highest north-facing slopes, creating weak surface snow during the heat of the day. Crusts may form overnight. 

 Strong solar radiation and warming will likely trigger the large cornices that hang over ridgelines. Cornice falls could trigger large avalanches on deeply buried weak layers. 

As heat penetrates deeper into the snowpack it has the potential to reactivate deeper weak layers, including a layer from mid-February and weak facets at the bottom of the snowpack. The most likely areas to be concerned about deeper weak layers are shallow parts of the region along the eastern slopes of the Rockies like Core Lodge, Wolverine, Bullmoose, Upper Burnt and perhaps around Mt. Robson. In general, steep, rocky slopes with a shallow or thin to thick snowpack are most suspect.

Terrain and Travel

  • Avoid travelling on slopes below cornices.
  • Avoid exposure to sunny slopes, especially in the afternoon.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.

Problems

Cornices

An icon showing Cornices

Likelihood

Likely

Expected Size

2 - 3

Cornices are large and will weaken with daytime warming. Stay well back from them on ridges and avoid travelling beneath them. A cornice fall has the potential of triggering slabs on the slopes below.

Aspects:

North, North East, East, North West.

Elevations:

Alpine.

Loose Wet

An icon showing Loose Wet

Likelihood

Very Likely

Expected Size

1 - 2

The snow surface will weaken over the course of the day as warm air and sunny skies prevail. The most likely areas to get into trouble are above terrain traps.

Aspects:

All aspects.

Elevations:

All elevations.

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

Likelihood

Possible

Expected Size

2.5 - 3.5

A prolonged period of warm air and sunny skies is heating the snowpack, increasing the likelihood of reactivating buried weak layers. It is uncertain if and when large slab avalanches may release, but the possibility remains during this warm period. Deeper releases are most likely in shallow snowpack areas along the eastern slopes of the Rockies.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Valid until: Apr 17th, 2021 4:00PM

Forecast Trend

The latest forecast danger ratings, broken down to elevation. See how an elevation is trending.