April 17, 2012 Posted by Emily in Explore, Lifestyle
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House of Cards

By Scotty Savage Explorebigsky.com Avalanche Expert

Most years, spring skiing and riding means a carefree day in the mountains enjoying tasty turns and soaking up rays. Picture yourself ripping the corn or climbing a perfect bowl with a dusting of new snow on a bomber crust—are you thinking about big, wall-to-wall avalanches that take out entire bowls or even cirques?

In nine years out of 10, deadly avalanches like that are a thing of the past come April, something that we worry about in the middle of the winter, right?

Here’s the problem: Like drawing an inside straight to win a hand of high stakes poker, this is that rare spring when we still have to pay close attention to avalanche conditions.

Why? Repeat after me: Weird weather makes weird avalanches.

This winter’s weather has been weird by just about any measure. We started out the season forming an especially nasty layer of sugary, faceted snow crystals near the ground in November. The dry early winter conditions helped the facets grow weaker, leading to several dry slab avalanche cycles when it finally started snowing. The snows picked up in February and March, producing more avalanche activity. And we were still seeing avalanches failing on the same pesky facets during the last big storm cycle just a few weeks ago—over 120 days after they formed.

The snowpack around Cooke City is deeper and the facets have strengthened significantly, but the entire season’s snowpack is still sitting on top of this house of cards, the November facets, on many other slopes in southwest Montana.

Any guesses what happens when the “cards” get wet for the first time? These sugary facets lose strength and can produce wet avalanches like the activity at Bridger Bowl in late March.

The snowpacks on many slopes—especially those above treeline—haven’t gotten wet all the way to the ground yet this spring. Once snowmelt or rain thoroughly wets them, drainage channels form and large wet snow avalanches become extremely rare. This is why wet avalanche activity peters out in May most years.

We’ll need to be cautious during extended warm spells while these drainage channels are forming. What can we do to stack the odds in our favor in this odd avalanche year?

• Maybe this isn’t the season to ski that peak or gnarly line that you’ve been salivating over for years. It’ll be there next year.

• Pay attention to overnight temperatures. Many wet avalanches occur after consecutive days without freezing temperatures. NRCS Snotel sites are great sources for temperature information (wcc.nrcs.usda.gov/snotel/Montana/montana.html).

• As a longtime Big Sky ski patroller likes to say, “keep your head on a swivel.” When the sun is shining, pay attention to changing conditions. Snowballs rolling down steep slopes, sinking deep into the snowpack as you boot pack, and small slushy avalanches are signs that you should move to cooler slopes.

• Big storms still deserve respect. They may activate those ugly facets at the bottom of the snowpack. Give the snowpack some time—think days rather than hours—to adjust to large dumps before playing on steeper, more exposed slopes.

• If you have to get on the big exposed alpine slopes, you might wait for at least a few cold dreary days with below freezing temps and little or no additional snow. A few inches of snow on top of a rock hard crust will probably soften the surface without stressing the deeper faceted layers, stacking the odds of success in your favor.

Unfortunately, snow and avalanches aren’t as simple as we’d like them to be. Legendary avalanche forecaster Ron Perla once said, “The only rule of thumb in avalanche forecasting is there are no rules of thumb.” That’s true, except that weird weather makes weird avalanches.