Avalanche Forecast
Issued: Apr 5th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Cornices, Wind Slabs and Loose Wet.
swerner,
Avalanche Canada
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: Mix of sun and cloud. Ridgetop wind light from the southwest. Alpine temperatures near -2 and freezing levels 2000 m.Â
Wednesday: Mix of sun and cloud with isolated flurries. Ridgetop wind moderate to strong from the southwest. Alpine temperatures -2 and freezing levels 1600 m.Â
Thursday: Mix of sun and cloud with a trace of new snow. Ridgetop wind light from the southwest. Alpine temperatures near -6 and freezing lvels 1700 m.Â
Avalanche Summary
Cornices have been reactive in the last few days both to explosives and naturally, occasionally triggering wind slabs on slopes below.Â
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 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.
- Be alert to conditions that change with elevation and sun exposure.
Problems
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
Expected Size
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
Expected Size
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
Expected Size
Valid until: Apr 6th, 2021 4:00PM
