Avalanche Forecast

Issued: Apr 10th, 2023 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Deep Persistent Slabs.

Avalanche Canada bchristie, Avalanche Canada

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Observe your local conditions, and let that guide your terrain choice. As the freezing level falls, you will find that conditions change drastically with elevation and through the day.

Carefully choose the terrain you play in. A weak, unpredictable layer continues to lurk near the bottom of the snowpack.

Summary

Confidence

Moderate

Avalanche Summary

On Monday, near Golden, explosives avalanche control produced a few large (size 2) storm or wind slab avalanches, and one very large (size 3) deep persistent slab avalanche. These avalanches occurred on rocky or treed ridge features.

West of Invermere, a large (size 2.5), naturally triggered loose wet avalanche was reported that likely started just below treeline, and buried a road cut 2-3 m deep.

On Thursday, north of Golden, just outside of the forecast area, a large (size 2), rider triggered, deep persistent slab avalanche was reported on a northwest aspect in the alpine. The avalanche started 50 m above the riders, and 2 sympathetic avalanches were observed on the adjacent slope. See the excellent Mountain Information Network (MIN) post here for more information, including photos, and reflections on a close call.

Snowpack Summary

15-30 cm of recent snow in the alpine covers settling, dry snow on shaded (northerly) aspects, and a frozen crust on solar aspects. At treeline, the recent snow is likely to be denser, shallower, and moist or refrozen.

Below treeline, rain soaked surfaces are starting to freeze as temperatures drop, and a lot more dirt is showing at low elevations.

The mid snowpack is generally settled and strong, although west of Invermere, some professional operations are still monitoring a layer of weak, feathery surface hoar crystals that was buried in mid January.

The lower snowpack includes a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for several very large and destructive avalanches throughout the season, including one last Thursday.

Weather Summary

Snow/Rain amounts for the ongoing storm are uncertain. Weather models are not agreeing on how widespread or intense the precipitation will be, and exact freezing levels will be hard to forecast as they drop. Prepare to continually evaluate the conditions, and change plans as necessary.

Monday Night

Cloudy. 5-10 cm of snow expected in the alpine. Snow/rain line drops to 1000 m further north, 1700 m further south. Light northwest or southwest ridgetop wind, trending to moderate at high elevations.

Tuesday

Mostly cloudy, possibly sunny by the afternoon. 2-5 cm of snow expected as the snow line drops back to valley bottom. Treeline low around -3°C. Light southwest ridgetop wind, trending to strong at high elevations.

Wednesday

Partly cloudy. Possible trace of snow/rain expected. Freezing level at valley bottom overnight, rising to around 1700m. Light northwest ridgetop wind.

Thursday

Mostly sunny. No new snow/rain expected. Freezing level at valley bottom overnight, rising to around 1700m. Light variable ridgetop wind.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be alert to conditions that change throughout the day.
  • Be alert to conditions that change with aspect and elevation.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm totals are expected to reach 15-30 cm in the alpine by the end of the day on Tuesday. As freezing levels fall, it will start to snow at lower elevations.

Strong southwest winds at high elevations could be building deeper, more reactive pockets of slab in leeward terrain.

Storm slabs in motion may step-down to deeper layers in the snowpack that may have been weakened by rising temperatures and/or rain.

Use extra caution around ridgecrests, rolls, and on convex slopes. Retreat to mellower terrain if you find signs of instability like shooting cracks, whumpfs, or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

The base of the snowpack remains very weak. Avoid thin, rocky start zones and shallow areas with variable snowpack depths.

Deep persistent slab avalanches continue to be reported in this forecast area. See the avalanche summary for details of a deep persistent slab avalanche that were kindly shared by some backcountry users who had a close call.

This is a low-probability/high-consequence avalanche problem, and managing it is very tricky.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2.5 - 4

Valid until: Apr 11th, 2023 4:00PM

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