Rattlesnake

New snow and strong winds built small fresh wind slabs that skiers and riders could trigger on upper elevation east aspects. Signs of instability like shooting cracks warn you of dangerous conditions. The best way to mitigate this problem is to avoid wind-loaded slopes over 35º. 

After a beautiful sunny weekend, a cold front moved through yesterday, bringing strong west winds and light snowfall to the region. The Central Bitterroot received the most snow yesterday, and there were reactive fresh wind slabs growing at upper elevations. In the Rattlesnake and East Lolo area, there was less fresh snow, and wind slab development was limited. 

Showery snowfall continued overnight, but the wind died down to light to moderate. Snow totals thus far are variable due to the showery nature of the snowfall. The Central Bitterroot has been the winner with 8 inches of new snow at the Twin Lakes SNOTEL. In the Central Bitterroot, triggering a wind slab is likely, and the hazard may be Considerable at upper elevations. Other areas in the region have only received 1-3 inches. Today, we can expect light to moderate northwest winds and continued light snow showers accumulating 1 to 5 inches. The Rattlesnake and Central Bitterroot are favored for the highest snow totals. In areas that receive the most snow, wind slabs will grow along upper elevation ridgelines and cross loaded gullies. Wind slabs yesterday were found low on slopes due to the very strong winds. With lighter winds today, they will grow near ridge tops. 

A crust facet combo buried 1-2 ft deep has been found in isolated locations in the Bitterroot. Yesterday it was found on a middle elevation east aspect in the East Lolo area. Over the weekend, it was found on an upper-elevation north-northeast aspect in the Southern Bitterroot. Last week, observers found it on upper elevation south aspects. There is uncertainty regarding the sensitivity and spatial variability of this layer. It has produced propagating snowpit test results, but signs of instability have been limited. It appears to be most sensitive in shallower areas at middle and upper elevations, like around wind-swept ridges. It is worth investigating the snowpack by digging a snowpit before you commit to steep terrain. Be prepared to change objectives if you find unexpected unstable results or signs of instability like whumpfing or cracking. 

Today’s fresh wind slabs are a hiccup in a general trend of improving stability. Skiers and riders have been stepping out into bigger terrain. However, in the last week, there have been several unintentionally triggered avalanches. Thankfully, everyone involved has avoided injury or burial. We still have a dry mid-winter snowpack with isolated weak layers. Remember that even a small avalanche can have serious consequences in unforgiving terrain. Do your homework before committing to steeper slopes, and use safe travel practices, such as riding one at a time. 

Please let us know what you find out there by submitting an observation.

Ski and ride safe.