The idea of spring skiing conjures up beautiful images of corn-skiing, parking-lot beers, and long-awaited toasty temps. All these things are true, but backcountry skiers need to consider one other huge factor arising in the spring: wet avalanches.
Wet slides (available in two flavors, loose and slab) are an incredibly dangerous hazard that can arise anytime the snow warms up. And, of course, springtime is primo snow-warming time. Yet this mega-hazard is often an afterthought mentioned in avalanche discussions. “Oh yeah, and in the spring, you gotta watch out for wet slides.” … Yeah, those monster rivers of exceptionally heavy snow careening down a mountainside, snapping trees in half and pulverizing everything in their path. Watch out for those.
While wet slides are scary, they have the benefit of being fairly avoidable. Here we’ll give a super-quick overview of what’s happening and how to stay well away.
For most of the winter, the snowpack is building steadily in layers. Some are soft and fluffy, some are wind-hardened, some are crusty, and they may or may not be bonded well to one another. But then, come spring, the warming temps and strong sun start to affect the snow, melting its surface until it becomes wet, heavy slush. The problem with wet, heavy slush is that it’s very weak and has an awfully hard time clinging to the mountainside. In fact, as the snow gets saturated with water, it starts acting more like water would. It can break away and pour down the hillside in a powerful river of slush that hardens upon stopping.
Wet loose avalanches: a very uncool sluff.
A “loose snow” avalanche means the snow has “low cohesion”—which is to say, it’s not moving in one solid slabby mass. On cold mid-winter snow, we think of this as “loose sluff,” something to keep an eye on, but it has a certain fluffy feel. However, in the spring, we see wet sluff, which is extremely heavy and, thus, packs a punch.
As the American Institute for Avalanche Research and Education (AIARE) notes, “Loose wet snow avalanches … can be more destructive than loose dry snow avalanches, as the release can entrain denser, wetter snow with more destructive potential. Loose wet snow avalanches may be the trigger for larger, more destructive slab avalanches.” These suckers can not only sweep you off your feet and even carry you a distance, but they can also be the trigger for larger and more destructive wet slab avalanches.
How do they happen? Rapid warming on the sunny snow surface, or rainfall, which saturates the snowpack—and both of these things are common in the spring. Making matters worse, if it stays above freezing overnight, the melting only continues, and the snowpack gets even swampier … and less stable.
Wet slab avalanches– total jerks.
Even scarier than wet loose avalanches are wet slab avalanches. They form when a cohesive layer of snow gets manky and wet enough that it can’t hold on to its bed surface any longer. (Remember how wet snow’s weak? Yep, that factor’s at play again.)
Wet slabs are shifty—they can freeze back up if the temps get low enough (such as at night time), then turn unstable again when it gets warm or rains. Typically we skiers think of rain on the snow surface as a total bummer snow-quality-wise, but in the backcountry it’s a major safety issue because wet slabs can rear their ugly heads.
“Rain on snow provides the most common trigger,” according to the AIARE. “Rain simultaneously weakens surface snow, provides additional load, and rapidly transmits heat back into the snowpack. Continued rainfall can percolate through the snowpack to a weak layer.”
As with wet loose avalanches, they’re emboldened by long periods of above-freezing temps. The snowpack stays warm and loses its cohesion and strength.
How to avoid these troubles and safely make it back down for a nice margarita.
Fortunately, with a little careful planning and terrain management, you can dodge the wet-slide dragons altogether. Look at the hourly weather forecasts before you plan your ski tours, and pay careful attention to when the temps are warming up. Note whether the snow refroze overnight, and whether it was a good solid refreeze.
You can time your travel for the morning (getting a famed “alpine start” before sunup) and try hitting your descent as the snow warms just enough to turn into pleasant granular corn. This corn phase is fabulous, with a pleasant-sounding swoosh at every turn. It precedes the dangerous saturated mank phase that signals wet slides.
Once the snow is becoming wet, heavy, sticky, or roller-balling, you have every indication it’s time to G.T.F.O. Now you want to be done with your ski descent and away from any overhead or adjacent steep slopes that could catch you if a wet slab breaks away.
Takeaways: know before you go!
This is, of course, a very informal and Geartrade-speak explanation of spring avalanche hazards. It’s a great idea to pursue formal avalanche education courses, and gobble up everything you can read on the matter, including the classic Staying Alive in Avalanche Terrain by Bruce Tremper.
In addition to gaining more formal training in spring avalanche hazards, think about other hazards that arise in the springtime, too. Bulletproof “slide for life” snow is very dangerous if you’re on a steep slope and lose your footing either while skinning, bootpacking, or skiing. This is the season to consider ski crampons, boot crampons, whippets, mountaineering ice axes, or some combination thereof, depending on what kind of terrain you’re planning on covering.
The warming snow can also be awful to skin on, forming weighty clumps of “glop” caked onto your skins. This is a great time to pick up some Glop Stopper wax to apply to the skins to prevent or stop the problem. Pack your sunscreen, glacier glasses, light clothing layers, and a carefully selected IPA for your parking-lot debrief. And you’ve got everything needed for a great—and safe—time.
Shop for any of the safety equipment above here on Geartrade.com, and stay safe out there.
