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Avalanche Forecast

Archived

Jan 20th, 2023–Jan 21st, 2023

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

Regions

North Rockies, McGregor, Pine Pass.

Make conservative terrain choices and give the storm snow time to heal. There is some uncertainty in the intensity of Saturday's weather and how the snowpack will handle it.

Confidence

Low

Avalanche Summary

No new avalanches were reported in the past few days in the region but observations are limited.

If you are out in the backcountry please consider filling out a Mountain Information Network report.

Snowpack Summary

As a cold front passes over the region new snow will add to the storm slab problem. At lower elevations, a rain crust exists down 30cm, with reported elevations extending up roughly 1200 m.

Snowpack depths are shallower than normal, and several buried weak layers have been a concern over the past few weeks. One is a recently buried surface hoar layer found up to 60cm deep in sheltered terrain features at treeline and above. At this same depth, a crust exists on steep south facing slopes. Another layer of facets, crust, and surface hoar was buried around Christmas and is now up to 80cm cm deep. Finally, a layer of large, weak facets buried in November is found near the bottom of the snowpack. This layer is likely most problematic in alpine terrain, where shallower avalanches could scrub down to these basal facets.

Recent observations suggest the buried weak layers are gaining strength, but not enough to trust them in high consequence terrain.

Weather Summary

Friday Night

Stormy with 5 to 10cm of new snow expected. Strong southwest winds and a low of -3 at 1500m.

Saturday

Stormy with up to 15cm of new snow. Strong southwest winds shifting to moderate northwest and a high of -3 at 1500m.

Sunday

A mix of sun and cloud with light flurries bringing trace amounts of new snow. Moderate westerly winds and a high of -6 at 1500m.

Monday

Stormy with up to 15cm of new snow expected. Strong northwest winds and a high of -3 at 1500m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Be carefull around freshly wind loaded features.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

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.