Avalanche danger will spike higher than forecast on slopes that are being cooked by the sun.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
WEDNESDAY: Mix of sun and cloud with flurries. Treeline temperature near -10. Light south-westerly winds.THURSDAY: Mix of sun and cloud with flurries. A few cm snow overnight. Treeline temperature near -8. Light south-westerly winds.FRIDAY: Mix of sun and cloud with flurries. Treeline temperature near -5. Light westerly winds.
Avalanche Summary
No avalanches have been reported since Sunday, when several cornice falls were reported. Late last week, a very large deep persistent slab released naturally in the west of the region.
Snowpack Summary
Recent storm snow continues to settle and dry out. Variable recent winds have left behind wind slabs on many slopes at treeline and above. These are expected to heal within a day or two. Direct sun is likely to weaken surface snow layers and give cornices a bit of an extra nudge too.Persistent weak layers from early January and mid-December are still being reported by local operators. They are generally considered dormant, but could wake up with significant warming, a surface avalanche stepping down, a cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. They seem to be most concerning where they are associated with a sun crust on solar aspects. Facets linger at the base of the snowpack.
Problems
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.
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.