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 13th, 2019–Jan 14th, 2019

Alpine
Natural avalanches possible, human triggered probable.
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

Lizard-Flathead.

Slab avalanches may be increasingly sensitive to human triggering in the alpine Monday as warm temperatures reach their apex. Minimize exposure to steep slopes receiving direct sunshine.

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

A classic temperature inversion will be with us through Monday evening.  No significant precipitation is expected until possibly Friday.SUNDAY NIGHT: Clear skies, temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 2000 and 3000 m, alpine temperatures between 0 and +5 are expected, light variable wind, no significant precipitation expected.MONDAY: Clear skies, temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 2000 and 3000 m, alpine temperatures between 0 and +5 are expected, light southwest wind at most elevations with moderate northwest wind at ridgetop, no significant precipitation expected.TUESDAY: Mostly clear skies, freezing level at valley bottom, light variable wind, no significant precipitation expected. WEDNESDAY: Scattered cloud cover, freezing level at valley bottom, moderate to strong west/southwest wind, no significant precipitation expected. 

Avalanche Summary

On Saturday control work produced wind slab avalanches to size 2 on northeast facing features.  A size 2 natural deep persistent slab was also reported on a south facing aspect around 2100 m.  We're very grateful that a group of sledders shared a fantastic MIN report about their near miss here.  A large avalanche was triggered on a thin, rocky, southwest facing feature near ridgecrest, the photos tell a compelling story about the structurally weak snowpack that exists in many places in the region.  On Friday natural avalanches size 1.5 to 2 were reported from northeast through northwest facing terrain at and above treeline. Control work produced storm slab avalanches to size 2.5 on similar aspects. Control work also caused cornices to fail on southeast facing terrain which subsequently produced storm slab avalanches to size 1.5.

Snowpack Summary

Warm upper-level air temperatures may be impacting the snow surface. You may find dry snow, moist snow, or possibly a frozen melt-freeze crust, depending on how warm the air temperatures are. The warm air may make storm slabs a bit more touchy, especially in the alpine. At the highest of elevations, wind slabs may still linger in lee and cross-loaded terrain features.The middle and lower portions of the snowpack are generally well-settled and strong. However, there still remain a few deeper weaknesses in the snowpack around treeline and alpine elevations. Professionals are still tracking a layer around 150 to 200 cm deep, composed of sugary faceted grains, feathery surface hoar, and a sun crust. The base of the snowpack may also still be composed of weak faceted grains.  These layers would most likely be triggered by humans in areas where the snowpack is shallow.

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.