The chance continues for a single backcountry rider or skier to trigger large and dangerous deep persistent slab avalanches at the upper elevations as well as smaller wind slab avalanches at the mid and upper elevations. As new snow and strong winds occur today, these slabs will increase in sensitivity and new shallow soft wind slabs will develop. Avalanches are unlikely at the lower elevations. Careful snowpack evaluation, cautious route finding and conservative decisions are essential for safe travel in avalanche terrain.
Large destructive slab avalanches with depths to five feet could be triggered on east through north to west aspects. These large slabs will be hard, and are likely to have crowns high up in the slide path although initiation may occur lower on the slope. These slabs will increase in sensitivity as they are further loaded by sustained snowfall and strong winds.
Recently formed wind slabs and new soft slabs currently forming during this storm event could be triggered today. The newer wind slabs could have depths as large as eighteen inches by the end of the afternoon with a slight potential for older slabs to trigger with depths of an additional two feet.
The National Weather Service has issued a Winter Storm Warning for Western Wyoming through 6 PM on Saturday. Strong westerly flow combined with ample Pacific moisture will bring another significant snowfall event to the region. Expect 12 to 24 inches of new snow in the mountains by Saturday evening. Strong southwesterly ridgetop winds at 20 to 30 miles per hour will accompany this snowfall. Overnight lows in the mountains will be near 20 before rising into the mid 20s during the day.The general avalanche hazard is expected to rise to HIGH. As the day progresses, the chance of triggering newly developed soft slabs will increase and become very likely by the end of the day. These slabs, which could also release naturally, are forming on faceted snow and could reach depths of three feet by Saturday evening. In terrain that held snow from early October, deep persistent slabs are likely to release naturally or be human triggered. In the Tetons, these slabs could have depths ranging from four to six feet. Slab depths are expected to be in the three to five foot range in the Greys River forecast zone and around two to four feet deep in the Togwotee Pass area. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED WHEN HIGH AVALANCHE HAZARD EXISTS.
