Some potential persist for skiers or riders to trigger hard wind slabs in very steep upper elevation avalanche starting zones. At the mid and upper elevations older persistent slabs lie upon buried layers of weak faceted snow and could be triggered by skiers or riders who venture into steep avalanche-prone terrain. Avalanches are unlikely at the lower elevations.
Pockets of wind slab formed by north to northwest winds could be human triggered in steep upper elevation avalanche starting zones. These slabs could be triggered to depths of 6 to 12 inches and could step down to deeper layers of faceted snow.
Persistent layers of faceted snow lie in the snowpack. Slabs laying on these layers vary from one foot to as much as four feet in depth. These older hard slabs could be triggered after initiation of a new wind slab, by a single person hitting a weak spot, or by larger loads such as snow machines.
A stronger upper level storm system will move into the northern Rockies tonight and bring snow to western Wyoming on Thursday. This may be the first of several storms to impact the area through the weekend.Snowfall is likely to develop overnight with several inches of accumulation possible by day break and another five to nine inches likely in the mountains during the day. Up to four inches of accumulation is possible at the lower elevations. Temperatures will be in the teens in the mountains and in the 20s in the valleys. Winds will be southwest at 10 to 20 miles per hour and are forecast to veer towards the west and increase during the afternoon hours.The general avalanche hazard is expected to be MODERATE in the morning and increase as the day progresses. The hazard at the higher elevations could increase to CONSIDERABLE in the afternoon. Loose snow sluffs are likely to release frequently on very steep slopes during this storm and could attain sizable volumes in areas that overhang confined chutes and couloirs. New soft slabs will begin to form and increase in size and volume. Existing persistent slabs will be loaded and could become unstable and increasingly sensitive to human triggers. Monitor conditions and adjust your travel plan accordingly. There have been five avalanche fatalities in the Rocky Mountain area during the past two weeks.
