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

Dec 18th, 2022–Dec 19th, 2022

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

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

New snow continues to put more load on weak buried layers.

Don't be enticed by fresh lines as there is potential for 'step down' and the creation of large avalanches.

Confidence

Moderate

Avalanche Summary

As of this writing, no new avalanches were reported in the last 24 hours. With the accumulation of storm snow, expect this to change.

On Friday large avalanches were triggered using explosives on north-facing treeline features.

On Thursday Several size 2 natural avalanches were observed in treeline terrain in the Elkford area. These avalanches likely occurred earlier in the week and failed on the mid-November surface hoar layer which is down around 40 cm in this area.

Persistent slab avalanche activity has continued to taper off but these layers will likely remain triggerable in specific terrain features.

Snowpack Summary

Around 30 cm of recent low-density snow overlies a thin sun crust on steep solar slopes and surface hoar and facets in sheltered terrain. Moderate westerly winds will more than likely redistribute this snow and formed wind slabs

A well-settled upper snowpack may overlie a spotty layer of surface hoar and a thin sun crust formed in early December, now buried 40 to 60 cm deep. The mid-November layer consisting of facets and surface hoar is now buried around 80 cm deep. However, both these layers can be found much shallower in the northern part of this forecast region. At the bottom of the snowpack, a thick crust sits on the ground.

At treeline, snowpack depths vary from 100 to 200 cm.

Weather Summary

Sunday Night

Cloudy, 5 to 10 cm accumulation, 25 km/h west wind, -25 C at 1500 m.

Monday

Cloudy with sunny periods, trace accumulation, 15 to 25 km/h northwest winds, alpine temperature of -25 C.

Tuesday

Cloudy with sunny breaks, up to 4 cm accumulation, 20 km/h east wind, temperature -25 C at 1500 m.

Wednesday

Mix of sun and cloud, trace accumulation, 20 to 25 km/h northeast winds, alpine temperature of -25 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the old surface.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • In times of uncertainty conservative terrain choices are our best defense.
  • Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
  • The new snow may require another day to settle and stabilize.

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.