Silver Valley & Bitterroot Mountains

Another day of above-freezing temperatures will soften the surface snow, and small wet snow problems may develop in steep and complex terrain. Adjust your route to favor aspects with a more supportable surface if you find yourself sinking into moist snow above your boot top. Continue to use safe travel practices in the mountains. 

Finally, the long anticipated shift in weather starts to unfold this afternoon, and we will enter a more active and wet period. The flip side is that this storm system initially comes in warm with high snow lines between 6000’-5000’. This means things will get worse before they get better- as in, expect rain before we get too excited about potential snow amounts. With the timing of the storm track, there will likely be little change in conditions during daylight hours today, but we can look forward to things picking up overnight and into Sunday.

Filed teams in the Selkirk Mountains yesterday covered some ground and continued to test the sensitivity of the buried weak layers that are driving the persistent slab problem. They found a common theme: The slab depth or slab stiffness above the weak layer is the main driver in propagating results vs. non-propagating results. This means that on slopes where wind created thicker slabs from drifting prior to the warm up are the most likely places to trigger an avalanche. This recipe can be found on more of the north side of the compass, with west, north, and east-facing slopes holding the highest potential to trigger a persistent slab avalanche.

As we keep gathering snowpack data to pin down the distribution of preserved weak layers, continue to have a healthy suspicion around all aspects at middle and upper elevations. Before the late January snowfall, all aspects had developed weak snow that got buried, whether that be facets or surface hoar. Recent warming on southerly aspects may have helped diminish some of the weak grains, especially at middle elevations. Because these weak layers are buried on average 6”-12” down, taking a few moments to dig in the snow and investigate the snowpack structure before committing to a slope is a quick endeavor. This can provide a helpful snapshot of what is happening right below you, and should be an ongoing process throughout your travels. You may not be able to find buried surface hoar directly below the ridge line, but it could be preserved a few turns down on the slope.

Cloud cover last night may have trapped warmer air and limited any radiational cooling. Surfaces may be softer than the previous several days, and temperatures will get above freezing in the mountains today. Monitor surface conditions, and if you are sinking into punchy wet snow, consider rerouting to lower-angle terrain or try to find a slope with a more supportable surface to avoid running into a small wet snow problem.

Once precipitation starts, it will be a game of temperatures cooperating by just a few degrees that decides how much snowfall we receive and where. This leaves us with a bit of uncertainty around how things will settle out, but regardless, a new load on the current snowpack will inevitably introduce change and raise the danger. Once things officially start to unfold, we will gain more clarity around how the snowpack adjusts to more weight being added.

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IPAC is now on the Avy app! View, submit, and share observations on the go using the AvyApp. Your backcountry observations are critical for building our avalanche forecasts. Avy provides a centralized location for core trip planning, and you can view streamlined, up-to-date avalanche and weather forecasts for your selected zone, using offline caching. Download Avy today - App Store and Google Play.