Banner Summit

Strong winds and new snow are creating sensitive wind slabs and will continue to do so throughout the day. These slabs may be forming in atypical locations, thanks to the nature of the wind. While many of these slabs will be small, some may be large enough to bury a person. Be alert to the consequences of being caught in an avalanche in the terrain you are traveling in.

Let's take a minute to think about the weather over the past few days, the avalanche activity we've observed, and the role that the wind has been playing:

On Thursday, a quick-hitting spring storm brought anywhere from 2-12" of low-density snow to our forecast areas. Periods of light to moderate wind were recorded during this storm. Friday, several human-triggered wind slabs were reported and numerous experienced parties (myself included) backed off their planned objectives in favor of less consequential, less exposed terrain. That night, wind speeds ticked up again and a new batch of wind slabs was generated. The next day (Saturday), Chris went out looking to see how these slabs were bonding in the Banner Summit area and I did the same in the Sawtooths. Although we both found that wind slabs were bonding better than they had the day before, observers on Titus Ridge and in the Banner Summit area triggered wind slabs in recently loaded terrain. Remember, the best indicator of avalanches are avalanches.

Yesterday, I headed to the White Clouds to have a look at the distribution of recent wind slabs. I observed a few recent, small wind slabs that had failed naturally and I chose to avoid areas with these slabs. By the early afternoon, wind speeds had begun to increase significantly, transporting what little snow was left to blow around. Across the valley in the southern Sawtooths, skiers on Imogene Peak reported that the wind was building a fresh batch of sensitive wind slabs and they triggered one of these slabs on a steep, north-facing slope. Again, the best indicator of avalanches are avalanches.

That brings us to today, Monday. As I write this, an unusually strong cold front is sweeping across our area, creating strong to extreme winds, some light snowfall, and plummeting temperatures. Wind direction will shift from SW to NW as this front passes and a few fresh inches of snow will provide some ammunition for these strong winds. Here are a few things to think about with these slabs:

• Wind speed is a critical variable when it comes to wind slab formation. When the wind blows as hard as it is blowing now, it tends to build slabs in atypical locations. 
• Shifting wind directions and new snow will mask the presence of older slabs that formed overnight and in the past days. This makes it difficult to identify where wind slabs exist using visual clues.
• The string of triggered slabs over the past 3 days is a great demonstration that we have some weak layers of snow buried in the upper portion of the snowpack. Many of these wind slabs formed on weak surfaces, including slick crusts, facets, or some combination of these. These types of interfaces don't always heal quickly.

Wind slabs are sometimes viewed as a "manageable" problem, and there are some instances where this is the case. When wind slabs are small and form in predictable locations we can easily identify them and avoid them. However, when several generations of slabs are built from winds blowing out of different directions and at different strengths this problem becomes much less manageable. When you're traveling in the mountains today you'll be well-served to keep the complex distribution of wind slabs on your mind. Don't let your freezing digits and the sandblasting wind distract you from the problem at hand.