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Avalanche Forecast

Archived

Mar 19th, 2020–Mar 20th, 2020

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

Regions

South Columbia.

Warm sunny weather continues. Use increased caution when slopes and cornices warm up throughout the day. Deeper weak layers may still persist. Make observations and assess conditions continually as you travel. 

Confidence

Moderate - Uncertainty is due to limitations in the field data.

Weather Forecast

Thursday night: Decreasing cloud, light west wind, alpine temperature -9 C, freezing level valley bottom.

Friday: Mostly clear, light west wind, alpine temperature -4 C, freezing level 1700 m.

Saturday: Mix of sun and cloud, light west wind, alpine temperature -7 C, freezing level 1600 m. 

Sunday: Increasing cloud, light west wind, alpine temperature -8 C, freezing level 1600 m. 

Avalanche Summary

Over the past several days, avalanche activity was reported as natural loose wet avalanches (size 1-2) running in steep, sun-exposed terrain in the alpine. Cornices were also observed failing naturally, primarily on north, northeast, and east aspects.

In the last week, there have been multiple reports of large (size 2-3) natural, human-triggered, and explosive-triggered avalanches releasing on the late February surface hoar layer. These avalanches occurred on a variety of aspects between 1700 m and 2300 m and were breaking 40-100 cm deep. 

The number of data sources for the region is diminishing as professional operations close. If you're spending time in the mountains, consider sharing your observations via the Mountain Information Network. Heightened diligence and conservative risk management is recommended at this time.

Snowpack Summary

On Wednesday, temperatures reached 0 C up to 2000 m with strong solar radiation. You can expect to find either moist surface snow or crust on sun-exposed slopes.

Snow from last week may sit on a weak surface hoar layer and a crust on steep solar aspects formed in early March. Moderate to strong northeast and east wind redistributed snow and formed wind slabs that may remain possible to trigger in isolated areas. 

A widespread weak layer of surface hoar from late February is buried 60-120 cm deep. Though there is a low likelihood of triggering an avalanche on this layer, the consequences of doing so would be high. Read more about surface hoar on our forecaster blog.

Terrain and Travel

  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Make observations and assess conditions continually as you travel.

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.