Avalanche Forecast

Issued: Apr 4th, 2021 4:00PM

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

Avalanche Canada ahanna, Avalanche Canada

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 Watch for cornices and wind slabs near ridgetops and be cautious on sun-exposed slopes. Moderate danger reflects conditions near Golden where recent snowfall amounts have been highest. Asses conditions in your riding area as you travel.

Summary

Confidence

Moderate - Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region.

Weather Forecast

Sunday night: Partly cloudy with isolated flurries. Light northwest wind. Alpine temperatures around -7. Freezing level 800 m.

Monday: Sunny. Light to moderate northwest wind. Alpine high temperatures around -1. Freezing level 2100 m.

Tuesday: Sunny with increasing cloud in the late afternoon. Light to moderate southwest wind. Alpine high temperatures around -1. Freezing level 2200 m.

Wednesday: 5-10 cm new snow. Strong southwest wind easing to light. Alpine temperature around -5. Freezing level 1800 m.

Avalanche Summary

Cornices have been reactive in the last few days both to explosives and naturally, occasionally triggering wind slabs on slopes below. 

A natural size 3 was reported on Thursday in the Dogtooth range. It was on a southeast aspect in the alpine and is suspected to have solar-triggered and run on the crust buried in mid-March.

Reports from Wednesday included small (size 1) wet loose point releases from steep solar aspects and explosive triggered wind slabs on north to east facing ridgetops.

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 may have seen some wind effect in immediate less of exposed alpine features. Reports indicate it 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 small surface hoar has 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.

Problems

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

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

Loose avalanches can be expected in the new snow 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 - Likely

Expected Size

1 - 1.5

Valid until: Apr 5th, 2021 4:00PM