The persistent slab problem is widespread and will likely trigger where the snowpack is shallow. Snowpack is deeper in the Icefields, but if you trigger it, the result is deeper and more destructive avalanches.Good riding found BTL in Parkers.
Weather Forecast
Forecasted snowfall amounts delayed and most intense precip observed in the later afternoon and expected to continue through the night expecting more then 10cms. Strong south winds are expecting to continue, decreasing over the day Friday. Temperatures to remain cool but freezing levels up to 2000ms in the Icefields. Broken skies in the pm.
Snowpack Summary
Maligne/Jasper: Variable snow depth above tree-line, relative to exposure. Average HS 70cm. Surface wind slabs and persistent slab down 40-90cm, very touchy, even on low angle slopes.Icefields: Variable snow depth above tree-line, relative to exposure. Average HS 120cm. Cornices and building wind slabs overlaying supportive mid pack and weak base.
Avalanche Summary
Previously noted large destructive avalanches noted in the Maligne Valley up to size 3, one measuring 900ms in length at the crown. Field team in the Icefields noted 3 avalanches on similar cross-loaded Alpine features, up to size 2.5 on south aspect. No other Alpine observations due to weather.
Confidence
Intensity of incoming weather systems is uncertain on Thursday
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.