A second day of rain and warm temperatures will weaken the snow and increase the danger of large, wet avalanches in steep terrain today. Location, size, and timing of wet avalanches are difficult and sometimes impossible to predict. Staying out of avalanche terrain is the most effective way to avoid a wet avalanche today.
Large, wet slab avalanches could be triggered naturally or from the weight of a person today on north through south aspects. Expect this hazard to increase progressively throughout the day as rain and warm temperatures return to the range.
As rain and warm temperatures continue to decrease the strength of surface snow, small loose wet avalanches are likely in steep terrain today. In some areas, precipitation this morning may begin as snowfall before transitioning to rain. As this transition occurs, expect the likelihood of loose wet avalanches to increase as well as a slight increase in avalanche size.
The summit of Washington reported 0.29 inches of rain yesterday with a high temperature of 39 degrees. Temperatures dropped below freezing overnight, but will rise above freezing again today accompanied by additional rain. This continuation of warmth and rain makes wet avalanches a possibility again today.
Yesterday, multiple loose wet avalanches and roller-balling were observed across our forecast area. Expect this trend to continue today as the bonds of snow grains near the surface of the snow are progressively weakened by rain and warmth. Loose wet avalanches can be slow-moving and appear harmless from a distance, however their power, weight, and ability to knock you over should not be underestimated.
Wet slab avalanches continue to be a concern on the eastern half of the compass rose as water continues to percolate into the snowpack. The two layers that were producing snowpack instability with a dry snowpack, are now a concern for this wet slab avalanche problem as well. The first layer of concern is a density change in the old wind slab that has been commonly found between 30 to 50 cm below the snow surface. This weak interface produced very touchy results before the rain and warmth, and now could become reactive if water reaches this layer. Below this remains the very hard ice crust formed from the February 22nd rain event. If moving water makes filters down to and runs upon this layer, lubricating the space between snow and ice, there is a possibility for large, wet slab avalanches.
Wet avalanches are notoriously difficult to predict and forecast for. It is worth respecting avalanche terrain (including runout zones) today as the mountain gains and drains significant amounts of water.
Thanks to everyone for taking the time to submit observations of snow and avalanche conditions, both inside and outside our avalanche forecast area. Please keep them coming.
The Lion Head Summer Trail is closed for the season due to avalanche risk. The Lion Head Winter Route is open.
