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Avalanche Forecast

Archived

Feb 8th, 2023–Feb 9th, 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 and human triggered avalanches likely.
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.

Regions

Glacier.

Moderate Southerly winds are reworking the recent storm snow.

Watch for overhead hazards: cornices, touring parties and wind loaded slopes, and limit your exposure.

Confidence

Moderate

Avalanche Summary

One solar triggered loose avalanche size 1.5 on Wednesday in the Portal avalanche path.

Small cycle of natural avalanches over Tuesday night, mostly size 2-2.5, with one isolated size 3.0.

Avalanche control on Tuesday was effective in producing widespread avalanches throughout the park, up to size 3.5, failing in the recent storm snow with large powder components.

Snowpack Summary

50-70 cm of warm, storm snow has created a widespread storm slab. Moderate SW winds during and following the storm loaded lee slopes, in open terrain treeline and alpine.

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

Unsettled weather continues as another low pressure system brings moderate snow Friday with SW winds.

Tonight: Cloudy w/clear periods, Alp low -11*C, light SW winds, FZL valley bottom

Thurs: Cloudy w/sunny periods & isolated flurries, trace snow, Alp high -5*C, Mod SW winds, 1300m FZL

Fri: Flurries, 20 cm, Alp high: -7*C, Mod SW winds gusting to strong, FZL 1300m.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be especially cautious as you transition into wind affected terrain.
  • Caution around slopes that are exposed to cornices overhead.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.