The diurnal melt-freeze pattern has taken hold of almost all the accessible snow on the East Side. Spring has sprung. The snow has warmed and a round of natural loose wet avalanches released as cold snow warmed for the first time throughout the weekend. More recently good corn skiing has been found at practically all elevations by mid-morning to mid-day. Ideal spring conditions involve a thin layer of large wet rounded snow grains on top of a firm and supportable crust layer. With overnight lows barely dipping below 32 degrees and daytime temperatures well above average the thawing has been rapid and early in the day. By afternoon you can find increasingly unstable snow conditions. Once the top of the snowpack thaws deeply enough for the skiing to suck it is also becoming wet enough that it loses cohesion with its surroundings and you can trigger loose wet avalanches. Snow that has gone through the melt-freeze cycle several times tends to resist sliding better than snow that is becoming wet for the first time. That’s why we’re seeing the most recent evidence of loose wet instability on high elevation northerly slopes where the snow has remained wintry the longest. By now almost all aspects and elevations have stronger spring snow. However, areas of colder snow were reported as recently as two days ago. So some higher elevation slopes are still transitioning and may slide under increasingly warm conditions. That doesn’t mean that lower elevation slopes can’t slide once they become wet enough to be unsupportable. Rocks and trees tend to reflect solar radiation back down and warm the snow around them even more, so loose wet avalanches often originate from these features. Under the intense spring sun even open slopes are becoming wet by the afternoon. Chances of afternoon thunder showers means there is also the slight possibility of rain which would further warm and weaken the snow. Wet snow usually needs a steep slope, steeper than about 35 degrees, to slide. Once moving, slushy snow can slide down to very low angled terrain. So regardless of where you're going to travel in the coming days, plan to be off of and out from under steep slopes before they thaw too deeply. Pinwheels coming from rocks and trees, or your skis, are often the first sign that the surface is losing cohesion. Boot-top penetration into wet snow is a good sign of instability. You can avoid the avalanche problem by starting early and moving to less steep, shady slopes away from rock outcrops before conditions deteriorate. If the skiing sucks because your sinking in too far, it’s probably becoming unsafe too.
