http://www.pc.gc.ca/apps/links/goto_e.asp?destination=http://www.facebook.com/MRGnationalparks/posts/608542575941919Touchy windslabs and persistent slabs exist in many areas. Although the clues of instability, such as whumphing, are becoming less obvious the potential for large avalanches will persist. Stay vigilant and be cautious in your terrain selection.
Weather Forecast
A ridge of high pressure will keep things clear and cold through Thursday. Today alpine temps should be slightly inverted with a high of -12, while valley bottom temps will stay around -17. Winds will become light at treeline and moderate at ridgetop today. Wednesday will be similar but slightly warmer. Thursday will become cloudy with flurries.
Snowpack Summary
Cold temps are facetting the upper snow, while N'ly winds are reverse loading slopes and creating windslabs. The Dec 17 surface hoar layer is down ~50-70cm and on top of a thick rain crust up to 2100m. This layer is widespread and highly reactive in many areas. The Dec 9 surface hoar is down ~ 70-90cm but is more spotty in distribution.
Avalanche Summary
Yesterday skiers triggered a size 2 skinning up Youngs Peak. The 1m deep windslab propagated 150m wide and ran 300m. No-one was involved. Over the past week there have been daily reports of rider triggered avalanches to size 2.0 failing on the Dec 17 surface hoar. Many of these have been remotely triggered, and sometimes triggering slopes overhead.
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.