Avalanche Forecast

Snoqualmie picked up a few inches of snow here and a few inches there over the last several days. This resulted in a generally strong and right-side-up snowpack. About 2’ of recent snow rests over a prominent crust buried on 1/26. Keep three items on your mind Thursday as you ascend to higher elevations. 1. Be leery of steeper convex slopes where you may be most likely to trigger a lingering storm slab. 2. Use caution around wind affected slopes. Look for signs such as textured surfaces and drifts to point out where the wind loaded the snow into potentially deeper slabs. And 3. Lingering slabs could be larger and easier to trigger if you travel near the tops of the higher peaks around the Pass.

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Look for loose wet avalanches at mid-elevations and on sunny aspects as you travel. A narrow band between 4500 and about 6000’ will experience the warmest temperatures they’ve seen since the recent snow accumulated. These slopes could produce loose avalanche during periods of peak warming or if the rain comes in earlier than expected. Filtered sunshine in the morning could make loose wet avalanches more numerous on sunny slopes. If you see new rollerballs or fan-shaped avalanches steer away from similar slopes. At the lowest elevations, several rounds of warmth and rain should limit any additional loose wet activity.

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.