Avalanche Forecast

Issued: Apr 18th, 2023 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

Email

A developing persistent slab problem may be primed for human triggering at upper elevations. Conservative terrain selection is critical, choose well-supported, low-consequence lines.

Lingering wind slabs may remain reactive to human triggers on leeward slopes in the alpine.

Summary

Confidence

Low

Avalanche Summary

No new avalanches were reported on Tuesday.

Observations are limited at this time of year, please consider sharing any information or photos you have on the Mountain Information Network to help guide our forecasts.

Snowpack Summary

20-40 cm of snow last week accompanied by south winds formed wind slabs on northerly aspects. The snow sits over wind-affected surfaces or a crust on south-facing slopes.

A weak layer buried in late March is down 30-50 cm and exists as surface hoar and facets on north facing slopes and a crust elsewhere. Test results showed that this layer may be reactive to human triggers in isolated locations where the layer is well-preserved and has a cohesive overlying slab. See MIN.

The middle of the snowpack is strong and contains numerous hard crusts. Near the ground, weak faceted crystals exist. There hasn't been avalanche activity on this layer recently, but it remains on our radar and may become active when we experience change, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Tuesday Night

Cloudy with 5-15 cm of new snow. Ridgetop winds 10-30 km/h from the south. Treeline temperatures near -5 and freezing level at valley bottom.

Wednesday

A mix of sun and cloud with isolated flurries. Ridgetop wind 20-40 km/h from the southeast. Treeline temperatures near -2 C and freezing level 1300 m.

Thursday

Mix of sun and cloud. Ridgteiop wind 30 gusting to 65 km/h from the southeast. Treeline temperatures near -2 C with freezing levels near 1400 m.

Friday

Cloudy with new snow 3-10 cm. Ridgetop wind 15-45 km/h from the southeast. Treeline temperatures near -2 C with freezing levels near 1400 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Wind slabs may be poorly bonded to the underlying crust.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Cornice failure may trigger large avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

Persistent Slabs

An icon showing Persistent Slabs

30-50 cm of snow sits above a layer of facets and surface hoar on shaded slopes. On other slopes, this layer is a crust with facets above. Whumfing and settlements in the upper snowpack have been reported on this interface as well as snowpack test results indicating that human-triggering this slab is possible. Avoid steep open slopes capable of producing large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Wind Slabs

An icon showing Wind Slabs

Lingering wind slabs may remain reactive to human triggers on lee aspects in the alpine.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

An icon showing Loose Wet

Even short periods of strong solar radiation may trigger wet loose avalanches on steep, sunny slopes.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Apr 19th, 2023 4:00PM

Join