‘Large to Very Large Avalanches are Expected’: Sierra Avalanche Center Issues Critical Warning
The Sierra Avalanche Center has issued a critical warning for backcountry travelers in the Sierra region Saturday, citing a high risk of large and potentially dangerous avalanches.
The combination of heavy, wet new snow and strong winds is expected to significantly destabilize the already weak layers within the backcountry snowpack, creating hazardous conditions. A natural avalanche cycle is anticipated to start sometime today and continue into tomorrow morning, with instability so severe that backcountry travelers could trigger avalanches measuring 2 to 6+ feet deep as early as this morning.
Due to the heightened risk, the center strongly advises against travel in or below avalanche terrain for the duration of today.
“Large to very large avalanches are expected over the next 24 hours,” wrote the Sierra Avalanche Center in its warning. “As wet heavy snow loads the snowpack, failures could occur on a variety of weak layers at various heights within the existing snowpack.”
The ongoing storm increases the probability of weak faceted snow failing around the Dec 19 rain crust or the depth hoar near ground level. Avalanches resulting from these deeper weak layers could reach a size D3, which is substantial and very dangerous.
Indications of unstable persistent slabs in the area include recent avalanches, cracking of the snow surface, snowpack collapse, or “whumpfing” sounds. These avalanches might be remotely triggered from low-angle terrain, whether above, below, or adjacent to steeper slopes.
Gale force southwest winds are contributing to the danger by drifting new snow into cohesive wind slabs on the downwind sides of ridge-top areas and into gullies, primarily above or near the treeline. Even below the treeline, wind slabs may form to a lesser extent due to the intensity of the winds.
Given these conditions, the Sierra Avalanche Center reiterates its warning: travel in or below avalanche terrain is HIGHLY discouraged today.
