Avalanche Forecast

This week promises the first major warming event in some time and with that comes uncertainty regarding when and how loose wet avalanche activity will manifest. After a cool start to the day, warming on Monday will start earlier in the day than on Sunday and may reach 6500 ft by the afternoon. We think this will initiate widespread loose wet avalanches in soft or previously soft snow, but with the small expected avalanche size we have kept the danger at moderate. Be especially careful of steep rocky slopes facing west, south or east. Monitor snow surfaces throughout the day, and keep an eye out for roller balls and pinwheels as signs of wet and weak snow surfaces. Move to shaded aspects or lower angle terrain to avoid the problem. If you start seeing evidence of larger loose wet avalanches, we may be further along in an anticipated avalanche cycle than we thought: In this case, dial back your terrain selection to avoid exposure to all slopes receiving direct sunshine steeper than 35 degrees. 

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.

Strong and variable winds redistributed recent storm snow into wind slabs at upper elevations. These slabs are getting old and should be stubborn or difficult to initiate, but you may still be able to trigger them with a large trigger on a steep convexity. Winds have come from a wide variety of directions since the last snow event March 10-11, so you will find wind-affected snow on a variety of aspects. Expect wind slabs to grow larger and easier to find as you gain elevation or move into more wind prone areas. Some of these slabs may be hard slabs that break widely and behind you, making them especially difficult to escape. Travel cautiously if venture into the alpine, and carefully look and feel for evidence of wind drifted snow. Take time to identify and avoid smooth pillow-like drifts, areas below cornices, or where you find firm over hollow snow. Defer to supported or less consequential slopes if you find signs of instability like shooting cracks.

Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.