Observations made yesterday on Mt. Tallac (Desolation Wilderness area) revealed widespread wet snow in nearly all areas by mid day. At 10am, wet snow up to 6 inches deep existed on all aspects below 7,000'. Above 8,000' significant wet snow was limited to solar aspects with up to 4 inches of wet snow on the surface with cold recent storm snow below. Only 1-2 inches of wet snow existed on the snow surface on northerly aspects above 8,000' at 1pm. Above 9,200', a cold unmelted snow surface remained on true N aspects at 1pm. Runnels existed in most areas below 8,000' on E-SE-S aspects indicating good drainage of free water out of the recent storm snow. In isolated areas runnels existed at higher elevations and were noted to extend all the way to the top of the E aspect Corkscrew avalanche path at 9,100'. Runnels existed only up to about 8,000'-8,200' in the upper Tallac Creek bowl which has a more NE to ENE general aspect. Naturally triggered roller ball activity over 1 foot in diameter was witnessed at 12:45 pm in upper Tallac Creek bowl on the ESE aspect N edge of the bowl around 9,000' to 9,200'. No recent roller ball activity was observed in areas where runnels existed (photos, more info).

Avalanche Concern #1: Warming Instability

A second night in a row has passed with very little to no snow surface refreeze expected in areas above 7,000'. With very warm air temperatures expected for today, areas of wet snow instability are expected to form by mid morning. Isolated areas of naturally triggered wet loose snow avalanches are possible today. The greatest areas of instability are expected to form on E-SE-S aspects at the mid and upper elevations in areas where drainage out of the upper snowpack is not well established. The absence of a significant weak layer within the melting upper portion of the snowpack is expected to keep wet slab avalanche activity unlikely to very isolated today. Glide cracks are expected to continue to open up in areas where a comparatively shallow snowpack exists over smooth rock slabs in areas that receive significant sun exposure. Areas of wet snow instabilities are expected to spread to northerly aspects today as well, mainly at the mid and lower elevations.

Avalanche Concern #2: Large Cornice Failure

Sudden collapse of large to very large sections of cornice remains possible today and will continue to present a significant hazard to backcountry travelers. The likelihood that cornice collapse will trigger a slab avalanche on the impacted slope below is becoming increasingly unlikely. However, the large multiple ton pieces of cornice debris falling and sliding down the slope below are sufficient to cause serious injury. Stay well back from the edges of cornices, preferably to the areas where exposed rocks are visible sticking up out of the snow surface. Reports of cornice failure up to 30' back from the edge have been received over the past few days. Avoid stopping or gathering with other backcountry travelers on slopes directly below large cornice features.