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Avalanche Forecast

Archived

Mar 16th, 2020–Mar 17th, 2020

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

Regions

Sea To Sky.

Avalanches will become more likely as the snow heats up. Be very cautious around cornices and large slopes getting hit by the sun.

Confidence

High - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

A ridge of high pressure brings clear dry conditions for the week.

MONDAY NIGHT: Clear skies, light northwest wind, freezing level drops to valley bottom with alpine temperatures dropping to -8 C

TUESDAY: Sunny with a few clouds, light northeast wind, freezing level climbing to 1500-1800 m in the afternoon, alpine high temperatures around -2 C.

WEDNESDAY: Clear skies, light northeast wind, freezing level climbing to 1500 m, alpine high temperatures around -2 C.

THURSDAY: Sunny with a few clouds, light wind, freezing level climbing to 1500 m, alpine high temperatures around -2 C.

Avalanche Summary

Over the weekend a few small (size 1) human triggered slabs were reported, primarily wind slabs in alpine terrain.

Looking forward, the warming trend poses a number of avalanche concerns including loose wet avalanches, cornice falls, and an increasing potential for the deep persistent slab problem to reawaken. The potential for triggering wind slab avalanches also remains possible in steep alpine terrain.

Snowpack Summary

Surface conditions are highly variable with a mix of crusts, moist snow, and hard wind slabs. The surface will become moist on sun-exposed slopes and at lower elevations throughout the day. The warm air coupled with strong radiation from the sun has potential to rapidly weaken the upper snowpack and cornices.

In the alpine, hard wind slabs may be found on all aspects due to variable wind directions. Recent wind has blown from the northeast, forming wind slabs in unusual south to southwest terrain features. In sheltered terrain, about 30 cm of settled snow may overly a melt-freeze crust and potentially small surface hoar crystals.

Weak faceted snow and melt-freeze crusts exist near the base of the snowpack in some of the region, particularly the eastern and northern parts. This layer is considered dormant, as it hasn't produced an avalanche since Feb 20. The likelihood of triggering this layer may increase during this warming trend.

Terrain and Travel

  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
  • Carefully evaluate steep lines for wind slabs.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.