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Avalanche Forecast

Archived

Mar 15th, 2021–Mar 16th, 2021

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

Regions

Lizard-Flathead.

Avalanche hazard will rise with daytime warming and solar input. Time your day to move off slopes before they get moist or slushy. Consecutive days in a row of warm temperatures may increase the reactivity of deeper weak layers and cornices.

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT: Partly cloudy, trace precipitation possible, wind light south east switching to south west, alpine low -3 C, freezing levels uncertain-especially around Fernie, 1000-1500 m. 

TUESDAY: Mostly sunny, light to moderate south west wind, alpine high +4, freezing level 2100 m.

WEDNESDAY: Sunny, light to moderate south west wind, alpine high +6, freezing level 2200 m.

THURSDAY: Increasing cloud, moderate south west wind, alpine high +8, freezing level 2400 m

Avalanche Summary

On the weekend wet loose avalanches size 1-2 were reported from alpine and treeline elevations. A couple of recent cornice falls from the last week have been noted as well. A small (size 1) wind slab was triggered accidentally near Fernie on Saturday. On Thursday-Friday a few solar triggered slabs up to size 2 were noted.

Snowpack Summary

Wind slabs in the alpine may linger, especially on northerly aspects. Snow on all solar aspects and elevation bands has been getting moist by mid morning and may not be getting the best overnight recovery if it is cloudy overnight. Reports suggest snow on north facing terrain above 1500 m has so far remained dry. Cornices are large and looming, and glide cracks are increasing in size...both should be considered unpredictable and given a wide berth.

Around 30 to 50 cm of snow overlies a variety of old interfaces that formed in mid-February. There hasn't been recent avalanche activity on this layer, but it remains on the radar, especially in alpine terrain as things stay warm. The late January persistent weak layer is found 50 to 100 cm deep. This layer is mostly composed of sugary faceted grains or feathery surface hoar crystals. In specific terrain features the layer is still producing snowpack test results causing some concern for low probability high consequence avalanches, especially in this periods of warming. 

Terrain and Travel

  • Be alert to conditions that change with aspect and elevation.
  • Cornices become weak with daytime heating or solar exposure.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.