North Rockies Avalanche Forecast

Issued: Apr 21st, 2021 4:00PM

Thu Apr 22nd Current Conditions
Alpine Moderate Treeline Moderate Below Treeline Low
Fri Apr 23rd 2 Day Outlook
Alpine Moderate Treeline Low Below Treeline Low
Sat Apr 24th 3 Day Outlook
Alpine Moderate Treeline Low Below Treeline Low

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

A spring diurnal pattern dominates. Wind slabs may exist up high. Danger may increase during the heat of the day.

Summary

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 5 to 15 cm and locally more with convective flurries, 40 km/h north wind, alpine temperature rapidly dropping from 0 C to -12 C.

THURSDAY: Morning clouds and afternoon clear skies, 20 km/h north wind, alpine temperature -10 C, freezing level 1000 m.

FRIDAY: Mix of sun and cloud, 20 km/h west wind, alpine temperature -7 C, freezing level 1500 m.

SATURDAY: Mix of sun and cloud, 20 km/h northeast wind, alpine temperature -9 C, freezing level 1200 m.

Avalanche Summary

Avalanche activity has quieted down since the heat wave last weekend. Large loose wet and wet slab avalanches were observed during daytime warming but no new avalanches were observed on Tuesday.

Looking forward, spring-like diurnal conditions are forecast to dominate after Wednesday night's storm. Wind slabs could form during the storm and they may be relatively easy to trigger, as they are likely going to overly a hard melt-freeze crust.

Snowpack Summary

Around 5 to 15 cm of snow is forecast to accumulate by Thursday morning. The snow is expected to fall with strong northerly wind, forming small but potentially touchy wind slabs in exposed terrain features at higher elevations. This snow will overly a hard melt-freeze crust to the mountain tops from recent warm air and sunny skies. The snow may moisten during the heat of the day, particularly on sun-exposed slopes and on all aspects below the freezing level.

A weak basal snowpack is found in many parts of the region, including 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 and should be avoided.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Avoid travelling on slopes below cornices.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

New wind slabs may be found in exposed terrain features. The snow may not bond well, as it will likely sit on a hard melt-freeze crust. Use caution as you enter steep, wind-loaded terrain features.

Aspects:

East, South East, South, South West, West.

Elevations:

Alpine, Treeline.

Cornices

An icon showing Cornices

Likelihood

Possible

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.

Valid until: Apr 23rd, 2021 4:00PM

Forecast Trend

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