Up to a foot of new snow with over an inch of moisture fell on Monday and Tuesday. This storm began warm and ended cold. It was accompanied by strong southwest winds that veered to the northwest. This snow accumulated on bare ground on west, south and east aspects at the upper elevations and on all aspects at the mid and lower elevations. On steep northerly aspects above an elevation of 9,000 feet this snow accumulated on faceted snow and crust that formed in October and early November. This buried old snow layer is up to six inches thick. Bitterly cold temperatures and clear skies have dominated the weather since Tuesday afternoon. The avalanche hazard is limited to very steep north facing terrain above an elevation of 9,000 feet.
Isolated pockets of wind slab up a to a foot in depth are unlikely to be human triggered but cannot be ruled out in steep upper elevation terrain where faceted snow exist at the base of the snowpack.
A winter storm warning has been issued by the National Weather Service for Teton County and the Absaroka Mountains until noon on Saturday. The remainder of the forecast area remains under a winter weather advisory. Periods of moderate to heavy snowfall will be accompanied by increasing temperatures and winds. New snow accumulations of 3 to 7 inches are possible overnight. Another 6 to 10 inches are possible in the mountains on Friday. Temperatures will rise into the 20s in the mountains and into the 30s in the lowest valleys. West-southwest winds will increase to 15 to 25 miles per hour with gusts in the 30s along the higher ridge crests.The incoming snow will be upside down (denser, warmer snow over lighter, dryer snow) and is not expected to bond well to the underlying cold, faceted snow. This scenario will be exasperated by strong winds that will create unstable conditions and an increasing avalanche hazard. The general avalanche hazard is expected to increase to MODERATE at the upper elevations. The danger will be most prominent on steep, north facing slopes above an elevation of 9,000 feet where strong west-southwest winds will create new wind slabs up to two feet in depth on a base of weak, faceted snow. These wind slabs are likely to become increasingly sensitive to human triggers as they gain depth and volume during the day. The general hazard at the lower elevations is expected to LOW but also on the increase. Evaluate terrain, monitor conditions and avoid areas of concern. Even small avalanches can have severe consequences in shallow snow conditions.
