Avalanche Forecast

Issued: Nov 19th, 2020 8:20AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

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Glacier.

This active weather pattern we are in has made for an active avalanche cycle in Glacier National Park. Consider overhead hazard traveling at lower elevations.

Summary

Weather Forecast

Today: Snow is forecasted to taper off to flurries, maybe 5 cm of accumulation, FL Hovering around HWY elevation, and mod SW winds

Tonight: Flurries, FL lowering to 700m, Moderate SW wind

Friday: 11cm of new snow, FL 1100m, Strong SW wind

Weekend: Cloudy with sunny periods

Snowpack Summary

40-90cm of Storm snow now covers the Nov 5th Crust, which exists up to 2500m on all aspects and higher on steep solar aspects. Reactive storm slabs have been observed in the upper snowpack at Alpine elev, and exposed areas of Treeline. Facets have also been observed on the Nov 5th crust, making for a excellent weak layer/bed surface combo.

Avalanche Summary

A modest natural avalanche cycle started yesterday morning, and is continuing today. Approx a dozen avalanches were obs in the HWY corridor in steep, unsupported terrain. Min reports from the Pterodactyl , Connaught drainage, and dispatches bowl of natural, and skier triggered avalanches. Storm and persistent slabs released to size 3.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Storm Slabs

An icon showing Storm Slabs

Recent new snow, warm temperatures, and strong wind has created storm slabs in the Alpine, and exposed areas of treeline. Natural avalanches are possible today, skier triggering remains likely, and very likely on steep unsupported terrain features.

  • Convex features and steep unsupported slopes will be most prone to triggering.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1.5 - 3

Persistent Slabs

An icon showing Persistent Slabs

MIN report from yesterday of skiers triggering storm slabs that stepped down to the Nov 5th crust. The storm snow above the crust is gaining cohesion and slab properties. We are getting into critical depths for skier triggering and large avalanches.

  • New storm slabs may step down to deeper layers resulting in large avalanches.
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Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Valid until: Nov 20th, 2020 8:00AM

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