The National Weather Service has issued a Winter Storm Warning through 5 PM today. The combination of very strong winds and over a foot of new snow has created dangerous avalanche conditions. This loading event has added weight to faceted weak layers below the new snow, and large to very large natural avalanches will be possible at the mid and upper elevations. Up there, skiers and riders are also likely to trigger new soft slabs and loose snow sluffs in steep avalanche terrain. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED ABOVE 9,000 FEET. A conservative approach to route finding will be essential for safe travel in avalanche terrain at the mid elevations. At the lower elevations, backcountry travelers could trigger isolated pockets of soft slab up to a foot deep in very steep terrain.
Abundant snowfall and very strong winds have loaded weak layers of faceted snow that formed during the mostly dry period from the first half of December. Below this faceted snow, stout crusts from the end of November provide good sliding surfaces, and backcountry travelers are likely to trigger slab avalanches ranging in depth from two to four feet. Natural activity can also be expected.
Skies will become mostly clear overnight as the arctic air mass continues to move south. As the day progresses, cloud cover will increase ahead of a Pacific weather system approaching the region. Overnight lows in the mountains will be in the negative single digits before climbing to near 10 degrees in the afternoon. Northwesterly ridgetop winds will back to the west overnight and decrease to 10 to 20 miles per hour.The general avalanche hazard is expected to be CONSIDERABLE in the mountains on Sunday. Skiers and riders could trigger soft slabs and loose snow sluffs involving the new snow in steep, avalanche prone terrain. The greater avalanche concern involves persistent weak layers of faceted snow which formed during the mostly dry period from the first half of December. While the likelihood of triggering slab avalanches failing on these layers is decreasing, the consequences remain high. Continue to make conservative terrain choices and avoid slopes that exhibit shooting cracks or whumpfing.
