With no refreeze Monday night, it will probably be very challenging to find terrain free of significant hazard on Tuesday.
Confidence
Fair - Freezing levels are uncertain on Monday
Weather Forecast
Synopsis: The ridging is looking a bit weaker today, but the freezing level is still forecast to top out around 2300m Monday, and its expected to remain there through Tuesday afternoon.Monday Night: Freezing Level: 2300m - 2500mTuesday: Freezing Level: 2300m - 2500m; Precipitation: Trace; Wind: Treeline: Moderate, SW | Ridgetop: Strong, SWTuesday Night: Freezing Level: 2500m lowering to 1300m; Precipitation: 4:8mm - 4:15cm;Wednesday: Freezing Level: 1200m - 1800m; Precipitation: Trace; Wind: Treeline: Light, W | Ridgetop: Moderate, WThursday: Freezing Level: 1200m rising to 2200m; Precipitation: Nil; Wind: Treeline: Light, Variable | Ridgetop: Moderate, W
Avalanche Summary
Wind slab avalanches ran to size 1.5 Sunday, with the bulk of the activity being reported from steep north through east facing terrain immediately below ridgecrest. In the central/east portion of the region a few small avalanches were triggered by skiers to size 1.5 on north through east facing features around 2300m. These were reportedly running on a thin crust from early April.
Snowpack Summary
Recent warm temperatures have resulted in good settlement and bonding of the storm snow from earlier in the week, but there are still isolated rider triggerable wind slabs on wind exposed north through east facing features.Three persistent weak layers exist in the highly variable snowpack of the Columbias:The mid-March sun crust/surface hoar layer down 50-80cm still has potential for human-triggering in isolated areas. The early-March crust/facet/surface hoar layer down around 80-120cm has become less susceptible to human triggering, but still has the capacity to produce large avalanches.The mid-February crust/facet/surface hoar combo is typically down 150 - 200cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up, which would result in very large and destructive avalanches.
Problems
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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.