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Avalanche Forecast

Archived

Mar 17th, 2020–Mar 18th, 2020

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, 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

North Columbia.

A ridge of high pressure has set in for the forecast period. Expect to see mainly sunny skies. Minimize exposure to steep slopes facing the sun during the hottest part of the day.

Confidence

High - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

TUESDAY Night: Mostly clear, light northwest wind, alpine temperature -8 C.

WEDNESDAY: Mix of sun and cloud, light northwest wind, alpine temperature -5 C, freezing level 1400 m.

THURSDAY: Mix of sun and cloud, light to moderate west wind, alpine temperature -6 C, freezing level 1400 m.

FRIDAY: Mix of sun and cloud, light northwest wind, alpine temperature -4 C, freezing level 1600 m.

Avalanche Summary

Avalanche activity on Monday was reported as natural loose dry or loose wet avalanches size 1-2 running in steep terrain facing the sun in the alpine.  

Reports from this weekend show several natural wind slab avalanches ranging in size from 1.5 to 3 running in the alpine on northeast, south and southeast aspects at treeline and in the alpine. There were also several cornice failures on northerly aspects to size 2.5.

Snowpack Summary

Recent moderate to strong northeast wind has created widespread wind effect in exposed terrain. With recent sun and relatively warm temperatures expect to find either moist surface snow or crust on slopes facing the sun. 30-50 cm of new snow from last week may sit on a surface hoar layer and a sun crust on steep solar aspects. 

A widespread weak layer of surface hoar buried at the end of February is 60-100 cm deep. On solar aspects, this layer may sit over a crust. There is a low likelihood of triggering an avalanche on this layer, but the consequences of doing so would be high. Read more about surface hoar on our forecaster blog.

Terrain and Travel

  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Cornices become weak with daytime heating.

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.

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.

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.