Northwest Mountains

The typically deep snowpack in the NW Mountains is holding up well, with very little avalanche activity over the last week. While this is confidence-inspiring, the snowpack still has buried persistent weak layers. Step out in your terrain choices cautiously, as it is still possible to trigger large destructive avalanches. You can reduce your chance of triggering a persistent slab avalanche, by riding areas with a consistently deep snowpack and avoiding areas where the snowpack thins to a below-average depth. Potential trigger points may be near rock outcrops or in areas where the snowpack depth varies, like in extreme or wind-affected terrain.

The most interesting observation yesterday was the beginning of the spring transition taking place at lower valley elevations from around 9,000ft and up to around 10,000ft in the SE Mountain forecast area. Above-freezing temperatures have combined with the strong March sun to rapidly settle and moisten the upper snowpack. The areas that were to most reactive, were locations that hold a weak snowpack throughout the winter and don't often have much for a slab above that weak snow. That type of snowpack is more typically found in the SE Mountain Forcast area, but that doesn't mean you couldn't find a shallow and transitioning snowpack somewhere in the NW Mountains. The avalanche danger at below treeline elevations is being held at CONSIDERABLE in the SE Mountains while these changes are occurring. High temperatures today may be a few degrees cooler than yesterday, before increasing into the weekend. 

The total snowpack depth is playing a key role in areas where the persistent slab avalanche problem is more or less reactive. In the last week, the bullseye for avalanche activity has been in the SE Mountain Forecast Area. During this period there have been 13 persistent slab avalanches documented in the SE Mountains and 1 persistent slab avalanche documented in the NW Mountains. Of course, we can't see every mountain and record every avalanche, so those numbers are never going to be perfect. Most notably we haven't had the best views along the spine of the Ruby Range. However, we have had enough views of both forecast areas to get a general sense of recent avalanche activity. Where the snowpack is deep, weak layers are both harder to affect with the weight of a person, and those buried weak layers continue to gain strength slowly. Where the snowpack is shallower, those weak layers haven't gained much strength and their shallower depth is easier to effect. It's difficult to put a number to what could be considered generally deep or generally shallow, as there are many variables. However, for some guidance, a deep snowpack where the persistent slab avalanche problem is less reactive and more difficult to trigger will have a total snowpack height of over 200cm. A shallow snowpack and somewhere where the persistent slab avalanche problem is more reactive will have a total snowpack height of less than 180cm.

Head on over to the avalanche observations tab and you can view plenty of recent and scary-looking avalanches that have occurred in the SE Mountains. It is great to see the NW Mountains holding up well without any recent avalanches to point to. Steeping out cautiously in the NW Mountains is a totally fair mindset. However, remember the possibility exists to trigger a large and destructive avalanche. We have a beautiful weekend coming up and it will be a lovely time to get out in the mountains. The snowpack will also feel that warm spring weather and strong March sun. As a result of the changing weather, cornices may fall and produce notable avalanches, or the likelihood for human triggering may slightly increase.