Dangerous avalanche conditions will be developing at the mid and upper elevations today. Strong winds are forming slab avalanches on a variety of old snow surfaces. Expert evaluation of terrain, the snowpack and rapidly changing conditions will be essential for safe travel in avalanche terrain. Shallow snow depths exist at the lower elevations and rain is forecast below an elevation of 7,000 feet.
At the mid and upper elevations strong southwest winds are creating dense wind slabs on leeward aspects. These slabs will gain depth and volume and become more sensitive to human triggers and natural releases as the days progresses. Slabs depths could reach 30 inches in the later afternoon and evening hours.
The National Weather Service has issued a Winter Storm Warning effective until 5 PM on Friday. A cold front will move through overnight and into Friday bringing periods of heavy snowfall. By Friday morning, an additional foot of new snow could accumulate in the mountains, and rain will turn to snow in the valleys. During the day, snowfall intensity will slowly decrease. Overnight lows in the mountains will be near 20 and only rise a couple of degrees during the day. Southwesterly ridgetop winds will veer to the west at 25 to 35 miles per hour.The general avalanche hazard is CONSIDERABLE and could increase to HIGH overnight depending on the amount of new snow and the impact of the wind. Abundant snowfall and strong ridgetop winds will continue to add depth and volume to newly developed wind slabs. Skiers and riders are likely to trigger these slabs ranging in depth from two to four feet in steep, wind-loaded avalanche terrain above 7,500 feet. This rapid loading event might be able to reactivate deeper slabs failing on old snow surfaces from October. This scenario would add an additional foot or two to slab depths. If the hazard does increase to high overnight, travel in avalanche terrain is not recommended.
