Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 31st, 2023–Feb 1st, 2023

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

Regions

Glacier.

Accumulating storm snow is building into a surface slab, which could step down to the lingering persistent slabs.

Less visited areas in Glacier National Park may have more sensitive persistent weak layers, due to less skier/rider traffic cutting up the slabs.

Confidence

Moderate

Avalanche Summary

Isolated sz 2 natural avalanches were detected from Smart Peak, Mannix, and MacD Gully 6 overnight.

Several human-triggered sz 1-1.5 avalanches were reported over the weekend on Avalanche Crest, Hermit Slide path, and Swiss Couloir.

A natural cornice failure triggered a size 3 deep persistent slab on the SE slope of Grizzly Peak on Saturday.

Snowpack Summary

15-20cm of storm snow sits atop old wind-affected surfaces in the alpine and treeline.

The early Jan surface hoar is buried 40-70cm and is most prevalent at treeline. The November 17th facet weakness can still be found near the base of the snowpack in many areas.

Weather Summary

Continuing flurries with moderate/strong winds aloft and a gradual warming to seasonal norms.

Wed: cloudy, flurries, 5cm snow, Alp high -9*C, light/moderate SW winds

Thurs: mix of sun and cloud, isolated flurries, Alp high -7*C, light/moderate SW winds

Terrain and Travel Advice

  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.

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.

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.