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Avalanche Forecast

Archived

Dec 11th, 2022–Dec 12th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Moyie, St. Mary.

Watch for signs of instability like natural avalanches, whumpfing, and shooting cracks as you travel through the terrain.

Wind slabs at treeline may have formed over touchy surfaces like crusts and surface hoar making them larger and more sensitive to triggering.

Confidence

Low

Avalanche Summary

No new avalanches have been observed or reported in this region. However, note that we have had very few field observations and much of our forecast has been extrapolated from our surrounding neighbours. Please consider filling out a Mountain Information Network report if you are heading to the backcountry.

Snowpack Summary

Saturday night brought another dusting to some parts of our region, ranging from 8 cm in the southwest to zero in the northeast. This adds to Friday night's totals of between 2 and 10 cm. These amounts came with minimal wind. Earlier in the week, southerly winds redistribute snow into wind slabs on west, north, and east aspects. A slight warming may help consolidate the fresh snow and produce a slab depending on the nature of the surface it is sitting on. There were reports of finding buried a layer of surface hoar 20 cm down in sheltered terrain and a sun crust on south-facing slopes.

A concerning layer of surface hoar from mid-November is buried down up to 40 to 60 cm. This layer could become more reactive as slab properties above it increase with new snow and wind.

Weather Summary

Sunday Night

Mostly clear, no accumulation, winds northeast 15 km/h, temperature -6 C at 1500 m.

Monday

A mix of sun and cloud, no accumulation, winds northeast 15 km/h, temperature -6 C at 1500 m.

Tuesday

Mostly sunny, no accumulation, winds northwest 10 to 15 km/h, temperature -5 C at 1500 m.

Wednesday

Cloudy with sunny periods, 2 cm accumulation, winds north 10 km/h, temperature -5 to -8 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.