North Columbia

10 cm of new snow and moderate northwest winds on Monday night may create fresh wind slabs on lee features at treeline and above. Larger, lingering wind slabs may remain surprisingly reactive to human triggers in areas where they are sitting on a layer of small surface hoar.  

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Avoid lee and cross-loaded terrain.

MONDAY NIGHT: Clearing skies / Moderate to strong, northwest ridgetop wind / alpine low temperature -14 / Freezing level valley bottom.

TUESDAY: Sunny / Light to moderate, northwest ridgetop wind / alpine high temperature -3 / Above freezing layer of air moving in late afternoon and creating a strong temperature inversion with warm air above roughly 2000 m.

WEDNESDAY: Sunny / Light, south ridgetop wind / alpine high temperature +1 / Strong inversion with an above freezing layer of air above 2000 m.

THURSDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature +1 / Strong inversion with an above freezing layer of air above 2000 m.

Check out this MIN of a recent human triggered wind slab avalanche at the Gorge.

If you get out into the mountains, please consider sharing your observations on the Mountain Information Network!

10 cm of new snow and moderate northwest winds on Monday night may create fresh wind slabs on lee features at treeline and above. 20-40 cm of recent storm snow and strong southerly winds created wind slabs at treeline and above that are now a couple days old. These wind slabs may remain surprisingly reactive in areas where they are sitting on a layer of small surface hoar. This layer has been described as “spotty” and may only be found in specific areas. A crust from early November exists down approximately 90-130 cm.   

This layer has been observed to have weak, sugary facets above and below it and is most likely to be reactive to human triggers on south facing slopes and in shallow, rocky, snowpack areas in the alpine.