Snow and SW wind on Saturday will be building new windslab conditions. Stick to sheltered slopes for best conditions.
Weather Forecast
The freezing level is only expected to drop to 1500 m overnight on Friday with possibility of heavy snow and moderate SW winds. Snow to continue through Saturday. Expecting a good recovery on Saturday night and light precipitation beginning Sunday night into the new week.
Snowpack Summary
Warm temps are developing isothermal conditions below tree-line and on solar aspects into tree-line. A persistent slab is bridging weak depth hoar at most tree-line locations. This slab will lose its support as temperatures rise and if overloaded by new snow. Thin rocky solar exposed alpine slopes are beginning to shed.
Avalanche Summary
No field trips on Friday. A large cornice triggered sz 3 slab avalanche on cross-loaded alpine NW facing slope was reported in the Icefields on Thursday. Numerous loose wet avalanches to sz 2 were observed in Portal Creek on Friday as sun heated the alpine slopes.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Saturday
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.