Gunnison

The spring transition continues on Thursday. As snow surfaces soften later today, slab avalanches are becoming more sensitive to human triggers, particularly on easterly- and westerly-facing slopes. The broader message remains unchanged; the snowpack structure is commonly poor on the northern half of the compass, and persistent slab avalanches remain possible to trigger with little or no obvious warning signs. While the likelihood of triggering has slowly decreased, the consequence if caught remains severe. Corn skiing on southerly-facing slopes is an excellent way to avoid the persistent slab avalanche problem, just don't overstay your welcome on steep slopes if you find yourself sinking deeply into a wet snowpack. 

Yesterday, a group unexpectedly remotely triggered a slab avalanche on a low-elevation east-facing slope. This avalanche failed on a small slope and remained small in size. One notable from the observation was that the group began noticing frequent signs of instability once the snowpack had warmed up in the afternoon. Another observation in the East River Valley on Tuesday found similar conditions in the afternoon. As the snowpack continues through its spring transition, slabs are softening and/or water is moving through the snowpack and further decreasing the strength of buried weak layers. This spring transition does follow trends, with specific aspects and elevations developing similar conditions before those conditions move onto other aspects and elevations as a warmup continues. Lately, that trend has occurred most commonly on lower-elevation easterly- and westerly-facing slopes, and on some higher-elevation southeasterly-facing slopes. Individual slopes will heat up at different rates, depending on slope angles and factors like rock outcrops that can pass more heat into the snowpack. In a few cases, we've observed meltwater reaching the weak layer and causing wet slab failures, which was likely the case in this partial burial above Coal Creek over the weekend.  We have had good overnight freezes, so water has recently been moving through the snowpack at a slower rate, and snow surfaces are well frozen in the morning. This freeze-thaw cycle has also made for some nice corn skiing on southerly facing slopes. 

The likelihood of triggering a persistent slab is decreasing at a snail's pace during our recent bout of dry, warm weather.  Because our snowpack was exceptionally shallow and weak until our mid-February storm cycle, snowpack structures often remain ugly and untrustworthy.  Stiffening slabs paired with surface crusts are making signs of instability and triggered avalanches harder to come by.  Terrain harboring poor structures is well defined by over 170 persistent slab avalanches in the past two weeks: west, north, east, and a few high southerly slopes.  The size is also well defined:  Any slab avalanches triggered this week will likely be large enough to bury, injure, or kill you.  Slabs are typically the largest and most difficult to trigger in the Ruby Range, and thinner and easier to trigger east of town and at lower elevations.  We were dealt a tough hand this winter.  Avoidance remains the easiest and most reliable strategy: heading towards lower-angle terrain or to aspects/elevations where the problem is unlikely: southerly aspects near and below treeline. Traveling on slopes where the snowpack is consistently deep and uniform, where surface crusts are thick and supportable, or where the problematic structures have avalanched away offers reduced risk but with greater uncertainty and serious consequences if your assessments are wrong.  

With another round of strong sun and warm temps today, there should be a nice window of soft spring conditions on southerlies. Don't outstay your welcome in steep terrain if the snow gets too mushy and wet; we've seen a few small wet loose avalanches recently.