Avalanche Forecast

Issued: Apr 6th, 2021 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

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Minimize exposure to large looming cornices weakening with daytime warming and solar radiation. Cornice fall could trigger a slab on the slope below.

Isolated pockets of wind slab may be found in immediate leeward features in the alpine.

Summary

Confidence

High -

Weather Forecast

Tuesday Night: Clear. Ridgetop wind light to moderate from the South and freezing levels 1200 m. 

Wednesday: Mix of sun and cloud with light snow 5 cm. Ridgetop wind moderate from the southwest. Alpine temperatures near -4 and freezing levels 1700 m. 

Thursday: Mix of sun and cloud with flurries. Ridgetop wind moderate from the West. Alpine temperatures near -7 and freezing levels 1400 m.

Friday: Cloudy. Ridgetop wind moderate to strong from the South. Alpine temperatures near -5 and freezing levels 1600 m.

Avalanche Summary

On Tuesday, wet loose pinwheels were reported from steep solar aspects.

On Monday, several wet loose natural avalanches were reported up to size 2 on solar slopes. Cornices have been reactive in the last few days both to explosives and naturally, occasionally triggering wind slabs on slopes below. 

The weather pattern is spring-like and fairly benign. Get after it early before daytime warming kicks in and solar radiation weakens the snowpack and cornices. 

Remember to stay well back from ridgetops that might be corniced and to avoid slopes with overhead cornice exposure especially under the current conditions where recent rapid growth and daytime warming has made them large and fragile. 

Snowpack Summary

The convective nature of Sunday's storm resulted in greatly variable snowfall amounts through the region, as much as 50 cm around Golden and 5-20 cm elsewhere. The recent snow was accompanied by strong southwest wind and may have formed isolated pockets of wind slab on leeward slopes at upper elevations. Reports indicate that the new snow is bonding well to underlying surfaces which include wind-affected snow in the alpine or crust on solar aspects and below 1900 m. Below this elevation and on solar aspects the new snow dusts crusty surfaces down to 1500 m. Below 1500 m, the moist snowpack is quickly diminishing.

A widespread crust layer from the mid-March warm spell can be found 30-60 cm deep, and a small surface hoar and facets have been observed at this depth on some isolated north-facing slopes. Reports suggest the snow is generally well bonded to these layers but isolated instances of large solar-triggered slab avalanches running on the crust have been observed. Deeper layers are strong and have been unreactive over the past few weeks.

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Carefully evaluate bigger terrain features on an individual basis before committing to them.

Problems

Cornices

An icon showing Cornices

Cornices become weak with daytime warming. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below. Their large mass can trigger deeper slabs on buried crusts in the upper snowpack that a single rider wouldn't trigger on their own.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

An icon showing Loose Wet

Wet loose avalanches may occur on steep solar aspects and at elevations where air temperature rises above freezing. Below treeline, loose wet avalanches are possible where snow did not refreeze overnight.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1.5

Wind Slabs

An icon showing Wind Slabs

Wind slabs will be most likely be isolated to immediate lees of ridgecrests and roll-overs in wind exposed alpine terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Apr 7th, 2021 4:00PM