Avalanche Forecast

Don’t overlook the huge volume of water we just received in a relatively short amount of time. Alpental’s weather station recorded close to 7 inches of water since late Friday night, and avalanche forecasters at WSDOT report that 14 inches of rain have fallen since the start of this month at road level. All of this water fell on top of the New Year’s Day crust, and several notable avalanches have been reported in the past few days as a result. Triggering avalanches will continue to be a concern, particularly above the rain line at ~5000 feet where precipitation was predominantly snow. With a cooling trend and more precipitation in the forecast, storm slab depths will continue to increase. Use caution on slopes 30 degrees and steeper, convexities, and unsupported slopes where you could trigger avalanches more easily. As temperatures continue to cool and more time passes, these avalanches will become less likely, but we are not there yet.

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.