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Avalanche Forecast

Archived

Mar 8th, 2020–Mar 9th, 2020

Alpine
Natural avalanches possible, human triggered probable.
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, human triggered possible.

Regions

South Rockies.

Storm snow may remain sensitive to human and even natural triggering Monday as the new snow feels the strong March sun for the first time. The new snow needs a bit of time to stabilize before we start gunning for the bigger objectives.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Enjoy the sun Monday.

SUNDAY NIGHT: Freezing level at valley bottom, light west/southwest wind, trace of snow possible.

MONDAY: Clear skies, freezing level rising to about 1500 m, light southwest wind, no significant precipitation expected.

TUESDAY: Clear skies in the morning becoming cloudy after lunch, freezing level rising to about 1500 m, moderate to strong southwest wind, no significant precipitation expected during the day, potential for 3 to 6 cm of snow at upper elevation Tuesday night.

WEDNESDAY: Broken cloud cover, freezing level holding at 1500 m, light to moderate west/northwest wind, trace of snow possible.

Avalanche Summary

In the neighbouring Lizard Range on Sunday loose dry and soft slab avalanches were sensitive to human triggering and control work to size 1.5. Avalanches there were 10 to 20 cm in depth, running fast and far. Similar conditions are expected to exist in the South Rockies & the storm snow may remain sensitive to human triggering Monday.

Snowpack Summary

The Friday/Saturday storm produced 20 to 30 cm of new snow which buried heavily wind affected surfaces in exposed areas as well as a sun crust that may be present all the way to ridge top on solar aspects. Temperature crusts extend up to about 1900 m on other aspects. This storm snow has not yet bonded to the old surfaces and is touchy.

A thick rain crust currently sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.

Terrain and Travel

  • The new snow could use a day or two to settle and stabilize before we start to tee up the bigger lines.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • Extra caution is needed around cornices under the current conditions.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.