Incoming storm will increase Avalanche Danger through Wednesday and Thursday
Weather Forecast
Warm, wet, pacific air is forecast to over-ride the arctic air Wednesday evening. This system may bring 25-30mm of precip with moderate winds and temperatures near -5C. The snowfall event is expected to last through Thursday evening.
Snowpack Summary
Moderate SW winds are adding to last week's windslabs in the usual lee locations. These formed from the 55cm of snow in the Icefields area over the last week. Mid-pack persistent weak layers, most notably Jan 7 surface hoar down 40-60cm and rotten Dec 15 facets sitting just below, remain the primary snowpack concern in specific areas.
Avalanche Summary
1 sz 3 natural slab avalanche was observed yesterday in a thin snowpack area in the Maligne valley on the NE side of Proposal peak at 2500m. Yesterday's road patrol noted older avalanches that were generally windslabs in the alpine to sz 2.5 and a few persistent slabs in the low alpine.
Confidence
Intensity of incoming weather systems is uncertain on Wednesday
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.