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Avalanche Forecast

Archived

Jan 17th, 2023–Jan 18th, 2023

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

Regions

Purcells, Esplanade, Dogtooth, East Purcell, St. Mary.

Continue to make conservative terrain choices and consider the consequences of an avalanche on a chosen slope. The snowpack remains weak and untrustworthy.

Confidence

Moderate

Avalanche Summary

A few small (size 1 to 1.5) human triggered slabs were reported on Monday, mostly failing on a 30 cm deep surface hoar layer. A few larger (size 2) human triggered slabs were reported in the Esplanade range. Explosive avalanche control produced multiple large (size 2) and one very large (size 3) deep persistent slab avalanches along steep rocky ridges at treeline. On Saturday, a skier triggered a size 2.5 avalanche on a low angle alpine slope near Golden. This avalanche had a 1 m crown and ran on the facets near the bottom of the snowpack.

Snowpack Summary

10 to 20 cm of settled storm snow can be found in sheltered areas, while open terrain has been wind affected. A rain crust can be found up to 2000 m in most parts of the region.

There are two concerning weak layers in the top meter of the snowpack. The first is a layer of surface hoar from early January and the second is a layer of surface hoar, facets, and a crust from December. Both these layers are most concerning at treeline and above. There is also a layer of large facets at the bottom of the snowpack that continues to produce avalanches and will likely persist for a prolonged period of time.

In general, the snowpack is shallow and weak.

Weather Summary

Tuesday night

Cloudy, no precipitation, 20 km/h west wind, treeline temperatures drop to -8 °C.

Wednesday

Cloudy, no precipitation, 30 to 40 km/h southwest wind, treeline temperatures around -6 °C.

Thursday

Mostly cloudy, isolated flurries with 1 to 5 cm of snow, 40 km/h southwest wind, treeline temperatures around -6 °C.

Friday

Mostly sunny skies, 30 km/h northwest wind, treeline temperatures around -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Uncertainty is best managed through conservative terrain choices at this time.

Problems

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.

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.