The snowpack at the mid and upper elevations and in isolated locations at the lower elevations has very poor structure. The recent snow has loaded a persistent weak layer and created conditions that are ripe for avalanche accidents. Large slab avalanches were remotely triggered by skiers yesterday. These dangerous slabs lurk on slopes that are familiar and enticing to skiers and snowmobilers. Some of these slopes are stable and some are not. In these conditions expert snowpack stability skills are not capable of determining individual slope stability. Excellent route finding skills that avoid slopes of concern and their run out zones are essential for safe travel today. Natural and human triggered slab avalanches have occurred in unusual locations.
Unstable conditions exit on slopes where recent new snow lies upon a persistent weak layer of faceted snow. Slab avalanches 1 to 3 feet in depth have been remotely triggered by skiers and snowmobilers. As these slabs slowly gain strength it is more likely that these slabs will fail after people are on them as opposed to while they are approaching them.
Clouds will increase overnight as the next Pacific weather system moves towards western Wyoming. Some flurries are expected over the higher elevations after sunrise. Steady light snowfall will develop by noon and increase in intensity in the afternoon. In the valleys it may briefly mix with rain. The snowfall will become heavy after midnight. Snowfall totals of six inches are possible in the mountains during the day. Temperatures will be in the single digits and teens overnight and rise into the 20s and 30s. Winds will back to the southwest and increase to 15 to 20 with gusts to 25 miles per hour.At the mid and upper elevations conditions remain dangerous. The recent new snow lies upon a persistent weak layer that is proven to be very sensitive to human triggers and can produce large avalanches in areas that are attractive to and frequented by skiers and snowmobilers. Our early season snowpack remains shallow. Suspect slopes have bed surfaces that are not fragmented by terrain features and anchors. Whumping and collapses have been wide spread and are sure indicators of snowpack instability. The new snowfall on Tuesday will be increasing the load on our buried weak layers and therefore increase the potential for suspect slopes to fail under the weight of a single person. Avalanche accidents are likely. Excellent terrain evaluation skills and conservative terrain choices are essential for safe travel in avalanche terrain. Finely tuned avalanche rescue skills are also essential.The general avalanche hazard is expected to be CONSIDERABLE above an elevation of 7,500 feet and LOW below that elevation.
