Avalanche Forecast

Wet slabs are incredibly difficult to predict and even harder to asses. That uncertainty, combined with their large and destructive nature, causes them to deserve a healthy respect. Give any avalanche path a wide berth Thursday, including where avalanches could run from higher elevations and travel into the forest below. We’re concerned about wet slabs during this forecast because of the dry and layered nature of the upper snowpack. There could be 1.5-3’ of dry snow sitting on a prominent crust formed over MLK weekend above 4500’. The elevation band where ample dry snow rests on the crust, that subsequently receives rain, will likely be the most dangerous Thursday and could produce the largest avalanches. Loose wet avalanches often occur in the same elevation bands as wet slabs and could act as triggers for slab activity.

Release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slab avalanches can be very destructive.

Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty

A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.

Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.

At lower elevations, the snow over the MLK crust is shallower and moist. As a result, we expect loose wet avalanches in these areas. New rollerballs and fan-shaped avalanche debris provide evidence that loose wet avalanches are likely. Look for the size and character of these avalanches to change as you ascend in elevation. Even loose wet avalanches could grow large enough to bury and kill you.

Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.

Several loose wet avalanches, and lots of pinwheels and roller balls.

Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.