West Slopes South

While an approaching winter storm will bring a change in the weather Sunday, the lit bit of rain and snow that may fall by the end of the day likely won’t create any significant avalanche hazard. Instead, firm and sometimes icy travel might be the most dangerous conditions you face. 

We’re expecting a winter storm to begin to impact the Pacific Northwest on Sunday. While you may see a little bit of rain and snow during the day, it shouldn’t be enough to pose any real threat. Instead, we’ll be left with cloudy skies, cooler temperatures, and increasing winds, all of which should help keep the snow frozen and all but eliminate any avalanche danger. By the end of the day, areas near Mt Rainier may receive a few inches of snow at mid and upper elevations. Other spots throughout the zone will likely only see a dusting. If more snow falls than expected, there could be a few very isolated wind drifted pockets near and above treeline. While these thin wind slabs may trigger easily, their small size should keep them from being very dangerous. 

Weeks of warm and often sunny weather created a very strong and well-settled snowpack. Moving forward, the current surface will likely be considered the “new ground.” Any avalanche issues should be near or above this interface. NWAC forecasters and avalanche professionals traveling in many areas of the West South zone this week reported a wide variety of snow grains and surfaces. “Variable” seems to be the word most often used. This will make predicting how any particular slope reacts extremely difficult. In general, a very strong and often icy melt-freeze crust formed on most SE-SW facing slopes at all elevations. On more shades aspects, weak near-surface facets and facet-crust sandwiches were seen. Spotty surface hoar, breakable crust, and wind-textured snow were also observed just to round out the variability. Above the rain-snow line, the storm snow will likely have trouble bonding well to any of these current surfaces. As a result, you may see small loose sluffs and very thin slabs fail after just a few inches of snow starts to accumulate. However, as the storm continues into Sunday night and Monday, this may cause the avalanche danger to increase significantly. 

The greatest risk you face on Sunday may come from challenging and sometimes icy travel conditions. During times like this, even a small slip can quickly turn into a long fall. Make sure you have the tools and skills you need to navigate these possibly dangerous slopes. While the new snow may help travel, this will take a while. On Sunday, a dusting of new snow may only hide the icy surface underneath.