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.

Moderate - Freezing levels are uncertain on Monday

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. 

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.

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.