Strong winds dominated the last storm cycle and triggering a wind slab avalanche will be possible on loaded leeward slopes and terrain features near and above treeline. Avoid cornices, convex pillows of wind-drifted snow, and steep slopes that have a continuous surface of harder, rounded, and rippled snow. At elevations below 10,000', generally low avalanche hazard exists. Small isolated pockets of instability may still be lurking, so avoid steep loaded slopes that are perched above gullies, canyons, and other terrain traps.
Anticipate avalanche danger to once again rise tomorrow as a significant winter storm tracks across Northern Arizona.
Predominant southwest winds have created wind slabs on leeward slopes, and terrain features over the last few days. However, on Saturday afternoon, winds shifted, creating loading on north and west slopes. Anticipate wind slab avalanches to be possible. Avoid wind-loaded, rounded, pillowed, rippled, or corniced slopes, as these may have new sensitive wind slabs.
Several facet and crust combos were widely distributed below the last storm and have been buried by the new snow. In addition, the new snow may be enough to re-energize the dormant persistent weak layer of basal facets on north and northeast aspects. Human-triggered persistent slab avalanches are possible, and wind slab avalanches may have enough force to step down to these layers, creating propagating failures on these weak layers. If so, these avalanches may become very large.
Before the last series of storms, sun crusts were observed at mid-elevations across the mountain on slopes with moderate to high sun exposure (E, S, W). Finally, the basal facets and depth hoar have been documented on northerly and northeasterly slopes between 11,000' and 11,800.' These basal facets have become less reactive as they have been buried deeper with strong slabs above them, providing additional support; however, the large amount of new snow in the last week could reenergize this layer.
The best way to manage the risk from persistent slab avalanches is to make conservative terrain choices and practice appropriate travel precautions.
Sunday, several wind-loaded pockets were reactive producing very small sloughs. These are signs of instability, and backcountry travelers should take caution and make conservative decisions when making tour plans and assessing terrain.
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