Confidence
Fair - Intensity of incoming weather is uncertain on Tuesday
Weather Forecast
Expect to wake up Tuesday morning with 10-15cm of fresh snow in the hills, but flurry activity is expected to taper off throughout the day. A building ridge of high pressure is expected to spread dry conditions Wednesday through Thursday morning before a frontalsystem arrives late Thursday bringing light precipitation. Freezing levels should remain near 1000m and winds should be light and variable throughout the forecast period.
Avalanche Summary
Loose surface snow may be susceptible to sluffing on steep slopes, but not expected to be particularly destructive unless terrain traps are in the runout. Deep persistent slab avalanches remain possible with heavy triggers in shallow rocky snowpack areas on unsupported slopes.
Snowpack Summary
By Tuesday afternoon, up to 15cm of fresh snow could be sitting on the widespread robust surface hoar created during the dry spell at the beginning of the month. This interface will be one to watch as it receives more snow load and/or the slab settles. Below that approximately 20cm of near-surface facets can be found on shady slopes while a sun crust can be found on southerly aspects. A well settled and strong snowpack sits on weak basal facets and depth hoar, which seem to be fairly widespread throughout the region. This deep persistent weakness was recently activated by warm temperatures, but cooler temperatures have once again reduced the sensitivity to triggers. Highly unpredictable glide cracks are also opening up, primarily on slopes with smooth ground cover. These full-depth gaping 'crevasses' could release without warning or act as a significant terrain trap.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.