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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

South Rockies.

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: Decreasing cloud, trace precipitation possible, light to moderate south west wind, alpine low -4 C, freezing level dropping to valley bottom overnight in most parts of the region.

TUESDAY: Mostly sunny, light to moderate west wind, alpine high +3 C, freezing level 2100 m.

WEDNESDAY: Mostly sunny, light to moderate west wind, alpine high +2 C, freezing level 2200 m.

THURSDAY: Mostly sunny, light to moderate southerly wind, alpine high +2, freezing level 2200 m.

Avalanche Summary

There were wet loose avalanches size 1-2 from south and west facing alpine terrain reported over the weekend.

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 a solid overnight re-freeze if there are some lingering clouds overnight. Reports suggest snow on northerly 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 60 cm of snow sits above a persistent weak layer of sugary faceted grains that was buried in mid-February. There have been a handful of avalanches that released on this layer in the past few weeks. There is another persistent weak layer that was buried at the end of January, found around 50 to 80 cm deep. This layer consists of feathery surface hoar, facets, and/or a hard melt-freeze crust. Periodic avalanches continue to be triggered on these layers by riders, particularly where a stiff wind slab sits above them. Check out this MIN that shows the positioning of the layers in the snowpack near Crowsnest Pass.

Weak faceted snow and a decomposing melt-freeze crust can be found near the base of the snowpack. 

Terrain and Travel

  • Be alert to conditions that change with aspect and elevation.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Cornices become weak with daytime heating or solar exposure.

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.