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Avalanche Forecast

Archived

Feb 7th, 2023–Feb 8th, 2023

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

Regions

Glacier.

Finally a decent winter storm rolled through Rogers Pass, modifying the snowpack and landscape.

Let the mountains settle into their new blanket of snow peacefully. Stick to supported, low-angled slopes with limited overhead exposure.

Confidence

High

Avalanche Summary

A natural avalanche cycle is currently underway Tues afternoon in Rogers Pass. Artillery control has been productive in the highway corridor, with average sz 2.5-3 avalanches from explosive triggers.

Snowpack Summary

70-85cm of storm snow from the last 6 days, strong SW winds, and mild temps have created reactive surface slabs.

The mid-snowpack is mainly rounded grains.

The basal Nov 17 deep persistent weak layer is mostly faceted with a decomposing crust in various locations.

Weather Summary

The tail-end of the atmospheric river leaves the area tonight, with unsettled flurries, gusty winds, and dropping freezing levels in its wake.

Tonight: flurries, 5-10cm, Alp low -12*C, mod/gusting strong W'ly, 400m FZL

Wed: isolated flurries, trace snow, Alp high -11*C, light SW winds, 700m FZL

Terrain and Travel Advice

  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Cornice failures could trigger very large and destructive avalanches.

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.