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Avalanche Forecast

Archived

Mar 3rd, 2021–Mar 4th, 2021

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

Rising temperatures may initiate wet loose avalanches and weaken cornices. Check steep or confined lines for wind slab or wet surface snow before committing and give cornices a wide berth from above and below. 

Confidence

Moderate - Uncertainty is due to difficult to forecast freezing levels.

Weather Forecast

Wednesday night: Mostly cloudy, moderate to strong south wind, freezing level rising to 1400 m.

Thursday: Mostly cloudy, 5-10 mm falling as rain at lower elevations starting in the afternoon, strong south wind, freezing level near 1300 m.

Friday: Overcast, 35-55mm of precipitation overnight and throughout the day falling as rain at lower elevations, strong southwest wind, freezing level and snow line dropping from 1500 m to 1000m.

Saturday: Increasing cloud, scattered flurries with up to 5 cm of snow above 700 m, moderate south winds, freezing level near 800 m. 

Avalanche Summary

On Tuesday, operators reported a small (size 1) wet loose avalanche on a south aspect. This avalanche activity is representative of what is expected given the warming temperatures and forecast precipitation on Thursday.

This MIN from Sky Pilot on Sunday describes cornice debris around 1600 m. 

There have been no reports of avalanche activity over the February 24th crust layer since last Thursday, when small to large (size 1-2) skier triggered avalanches in the storm snow were reported on all aspects.

Snowpack Summary

A rise in temperature and 5-10 mm of precipitation beginning in the afternoon on Thursday is expected to increase the potential for wet loose avalanche activity on slopes experiencing warming for the first time. Watch for pinwheels and roller balls, as they are a clear indication of this problem. You can avoid them by staying off steep slopes when the snow becomes wet or slushy. 

Strong south winds may contribute to wind slab formation in exposed areas above 1300 m, where precipitation may fall as snow. The combination of wind, temperature, and precipitation has the potential to weaken cornices.

30-40 cm of snow from the past week sits on top of a hard rain crust that exists all the way to the tops of the North Shore mountains. Reports indicate that the snow is adhering well to the crust. 

The snowpack below the rain crust is well settled and strong in most areas. Watch North Shore Rescue's snowpack update from Friday here.

Terrain and Travel

  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Carefully evaluate steep lines for wind slabs.

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.