Avalanche Forecast
Issued: Dec 23rd, 2018 10:05AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
NWAC,
Northwest Avalanche Center
The Mountain Loop area received significant new snow on Saturday night and Sunday. The storm slabs formed during this event are healing, but this takes time. You are most likely to trigger an avalanche as you go up in elevation, into areas affected by the wind, or on convex rollovers. We have no recent observations from this zone and the associated uncertainty should reduce your terrain selection.
Summary
Discussion
Avalanche Summary:
We haven’t received any recent observations of avalanches in Hwy 542 area, but visibility has been limited. To the south and east, a small wind slab avalanches were reported on an exposed slope at high elevation on 12/22 while storm slabs were becoming more reactive at Snoqualmie Pass with at least six observed 8” storm slabs triggered naturally or by humans on steep or unsupported slopes.
Problems
Storm Slabs
1-2 feet of new snow fell above 3500 feet within the past 48 hours in this zone. You can find weaknesses in the snow that are still capable of producing avalanches. If you are planning to travel near and above treeline or in areas where the wind affected the snow, you will still be able to trigger these soft slabs. At lower elevations and in wind protected areas, you are most likely to trigger a storm slab on convex rollovers, in terrain steeper than 40 degrees or on an unsupported slope. You can use smaller inconsequential test slopes to observe how the storm snow is bonding to the old snow.
When the sun comes out, expect small loose avalanches to occur on steep, rocky, sunny slopes. Don’t let them catch you off guard, especially if you are on slopes that could have dangerous consequences.
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.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 24th, 2018 10:05AM
