Boletín de aludes

South Rockies

Feb 26 – 27, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

Sun
Mon
Alta montaña
4 · Fuerte
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Lo esencial

Travel in avalanche terrain is not recommended on Friday. Natural avalanche activity may start to taper later in the day, however; slopes remain primed for skier and rider triggering. 

A Special Avalanche Warming is in effect for this region. 

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible - Likely
    Tamaño
    1.5–2.5

    Around 50 to 80 cm of snow overlies a buried weak layer of surface hoar, faceted grains, and/or a melt-freeze crust, depending on elevation and aspect. Reports to date suggest the Elk Valley and mountain ranges to the West of the region being the most problematic, but don't let your guard down elsewhere. Avalanches have occurred on surprisingly shallow slope angles.

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–2

    10-20 cm of new snow fell on Thursday with the heavier amounts in the southern parts of the region. This was accompanied by strong wind. This snow will build on slabs formed earlier this week. These storm slabs are likely around 40 to 70 cm thick south of Crowsnest Pass and 20 to 30 cm thick elsewhere. The slabs sit on sugary faceted snow formed during the cold spell mid-February. Keep in mind that strong wind will also form wind slabs in exposed terrain at higher elevations.

    Loose-dry avalanches may be easily triggered from steep terrain features, especially if the sun pokes out. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Friday: Snow amounts 5-10 cm with possible enhancements. Ridgetop wind moderate from the West and alpine temperatures near -5. Freezing levels rising to 1200 m by the afternoon.

Saturday: A mix of sun and cloud with possible flurries up to 5 cm. Ridgetop wind strong from West and alpine temperatures near -13. Freezing level at valley bottom.

Sunday: Cloudy with isolated flurries. Ridgetop wind extreme from the southwest and alpine temperatures near -8. Freezing level valley bottom.

Avalanche Summary

On Wednesday, this MIN report highlights a critical incident of a rider-triggered persistent slab size 3. Also on Wednesday, this MIN report indicates another remotely-triggered size 2 slab avalanche. Whether it's a wind slab or a persistent slab problem, they're catching folks by surprise and will not heal quickly. 

Looking towards Friday, human triggering of storm, wind, and persistent slabs will remain likely. Conditions are not easily managed right now, warranting a conservative mindset!

Snowpack Summary

Recent snowfall amounts vary across the region with 10-20 cm of new snow. Wind slabs are expected to build over the day in exposed terrain at treeline and alpine elevations. Storm slabs may continue to build in sheltered areas at all elevations. These slabs are expected to reach between 30 and 60 cm thick over the region and sit above sugary faceted snow formed mid-February.

A persistent slab 50 to 80 cm deep sits above a weak layer of surface hoar and may be found in sheltered terrain or otherwise faceted grains and/or a hard melt-freeze crust. This weak layer has recently been easily reactive to human triggers around the region. Check out this MIN report from yesterday in the Ruault Lake area in the western flank of the region. 

Weak faceted grains and a decomposing melt-freeze crust are likely found near the base of the snowpack. There have not been recent avalanche observations on this layer, but steep and rocky slopes, as well as shallow snowpack areas, should be approached with caution.

Terrain and Travel

  • Avoid exposure to overhead avalanche terrain during periods of heavy loading from new snow, wind or rain.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Choose simple, low-angle, well supported terrain without convexities.
  • The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.

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