Over the next few days cooling temps will lower avalanche danger. We are in a low probability, high consequence period. Large but difficult to predict avalanches continue to occur sporadically. Watch for solar warming and avoid cornices.
Weather Forecast
The ridge of high pressure will weaken briefly. There will be increasing cloud today, with isolated flurries. Temps should be slightly cooler, with a high of -4, and moderate but gusty westerly winds. Wed and Thursday will be similar. A mix of sun and cloud, light to moderate winds, with alpine high's of -5'C.
Snowpack Summary
Below 1900m a few cm's of snow sits on a hard crust. 15-20cm of snow sit on the Feb 18 surface hoar layer, which exists up to 2200m. The Feb 14 crust is down 20-25 and is up to 10cm thick. Variable wind effect, with pockets of thin hard slab, exists in exposed areas at treeline and above. Persistent weak layers down 1-1.5m are stubborn to trigger.
Avalanche Summary
Yesterday solar with an alpine inversion triggered numerous loose, solar triggered avalanches to size 2. Just outside the park boundary a solar triggered avalanche on a S aspect stepped down to deep persistent layers, propagating 400m wide and was a size 3.5. On solar aspects, small loose avalanches were triggered by riders, running on the crust.
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.