Although we have decreased the danger rating, heightened avalanche conditions exist on or below steep slopes. Triggering a slide remains possible and could result in a large avalanche that fails near the ground. Getting caught in a slide could have tragic consequences due to the exposed surface obstacles. Enjoy the new snow responsibly by sticking to slopes less than 30 degrees.
Recent snow has buried weak layers formed in mid-November. Slabs can break unexpectedly wide, deep, or be triggered remotely. Collapsing and whumpfing are indicators that you are in terrain with this weak snow structure. Choose slopes that are less than 30 degrees, free from overhead hazards, and build an extra margin of error into your riding lines.
Southwest winds have drifted snow into slabs 1-3 feet thick this week. Slabs can be found on the lee sides of ridges, in crossroads gullies, and downwind of saddles. Look for textured surfaces or pillows of snow that feel denser or hollow sounding. Signs of encountering these slabs are cracking beneath you and having your machine or boards ride on the snow surface. Triggering a surface slab may step down to a deeper buried weak layer resulting in a larger, more dangerous avalanche. Choose slopes sheltered from the wind and less than 35 degrees in steepness for a safer, more enjoyable experience.
We have dropped the avalanche danger rating this morning to MODERATE, Level 2 of 5. I would rate the hazard closer to Level 2.5 if we didn’t have to use whole numbers. Think of today’s rating as SCARY MODERATE. Scary because of the poor snowpack structure beneath the new snow that continues to provide feedback with collapsing or whumpfing sounds.
So why drop the hazard rating? The recent storm ended during the late afternoon or evening of Thursday, December 1. As of this morning, the snowpack has had 60 or so hours to adjust to the load. Several observations during the storm and the following morning reported remotely triggered avalanches and numerous collapses in the snowpack. Observers Saturday did not mention any new triggered slides or natural activity despite having good visibility to look at the surrounding terrain and skiing multiple laps. We must emphasize that most of Saturday’s observations noted multiple collapses, some of which were loud and rumbling. So the slab sensitivity is trending from reactive to stubborn. Stubborn, not unlikely or impossible.
Choosing the appropriate terrain is critical when dealing with a Persistent Slab problem. The chance of triggering a slide will increase as the slope angle approaches 35 degrees. Continue to choose low-angle terrain free of convexities or terrain traps. Avoid being under steeper slopes, as triggering avalanches remotely is still possible.
The weather forecast for Sunday is for warming and periods of sun. The storm snow has settled 7 inches at the Flattop and Shed 7 mid-elevation weather stations. Observers note that the once-light dry surface is becoming a bit slabby. Today’s warming may increase the density of the surface snow, which could contribute to cracking and possibly triggered slides. A slide at the surface could step down to a buried weak layer, resulting in a much larger avalanche.
Check out our new Observation View page. It highlights signs of instability and allows you to filter by date or zone, so you can pull out reports relevant to your objectives. We've updated our observation submission page as well. Try it out and help your community by sharing what you see in the backcountry. The form requires you to fill out the location fields and put a dot on a map. Be as vague or specific as you want.
Preseason restrictions on uphill travel are in effect at Whitefish Mountain Resort.
