Avalanche danger will spike higher than forecast on slopes that are being cooked by the sun.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
WEDNESDAY: Mix of sun and cloud with flurries. Treeline temperature near -10. Light south-westerly winds.THURSDAY: Cloud increasing. 5-10 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
On Monday, a few large slabs were reported. A size 3 persistent slab was remotely triggered by a skier in the east of the region. A couple more large naturally-triggered slabs were reported as failing on the February persistent weak layers on south to west aspects.
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.A couple of layers buried in mid-late February (down around 50-100 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, this interface was most reactive on solar aspects, where it presents as a buried sun crust. However, it has been triggered on shady aspects too, where surface hoar and/or facets exist.Deeper persistent weak layers from January and December 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. Facets linger at the base of the snowpack.
Problems
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.
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.