Wet slide questions thread

[mogul5480]

For obvious reasons, you don't hear nearly as much about spring wet slides as you do about their far more dangerous midwinter cousins. As a relative backcountry JONG, I've never even seen a wet slide in action, and have had a hard time finding information on how they're triggered, etc.

Has anyone ever heard of someone getting buried by a wet slide? If not, is one generally pretty safe travelling in wet slide conditions as long as one stays away from exposed terrain? Other than the obvious, are there any mitigating or contributing factors to the likelyhood of a wet slide coming down? Are there any good websites devoted specifically to this in detail?

Any guidance much appreciated. Thanks to all.

[Alpenglo]

Wet slides can be quite dangerous indeed. One of my first near-misses with an avalanche involved a wet slide early in my b-c skiing career and since then I treat them with a healthy dose of caution. They are hard to get out of and can entrain large amounts of snow, often involving the entire snowpack. If skiing slush was as much fun as powder, a lot more people would probably be involved in them.

Don't know offhand any websites dedicated to wet slides, although much has been studied and written in the scientific literature. Most books have a devoted section. The Avalanche Handbook, for one, is a great resource. I definitely recommend taking an Avy I course. If that doesn't answer your questions, take Avy II.

The good news about wet slides is they're more predictable. The key to avoidance is timing. Try to time your descent so that the surface is just barely softened/corned up. Always keep in mind, though, that barely softened up just below a summit may mean slushy, punchy, dangerous condition farther down the mountain. A good rule of thumb is, when the snow is starting to get punchy, i.e your skis are breaking through, get off that aspect/slope ASAP and try to find an aspect that is cooler and more supportive. Basically, corn = good, slush = bad. Hope that helps.

[CookieMonster]

Wet slides come in two flavours: loose and slab.

1. Wet, loose snow avalanches are similar to dry, loose-snow avalanches. Wet snow grains are held together by surface tension, not inter-crystalline bonds. With respect to skier triggering, wet loose-snow avalanches are triggered in the same manner as dry, loose-snow avalanches. Give the snow a little help moving downhill and things can get out of hand. Wet, loose-snow avalanches can entrain a lot of additional snow as they descend, large clumps sometimes form, and these avalanches can move very quickly. These slides are easier to predict because they're surface instabilities. The flowing snow is often very heavy.

2. Wet slab avalanches are similar to dry slab avalanches and may even have the same failure plane ( faceted crystals ) as a dry slab avalanche. The difference is that water is present in the weak layer or interface. Wet slab avalanches can involve the entire depth of the snowpack, especially if the snowpack/ground interface is smooth and wet. I'm not sure that much is known about forecasting wet slab avalanches, especially those that release by gliding.

3. "If not, is one generally pretty safe travelling in wet slide conditions as long as one stays away from exposed terrain?"

You're pretty safe traveling in any conditions as long as you avoid exposed terrain - hazard doesn't exist without exposure. Wet avalanches tend to travel more slowly than dry snow avalanches, but a high speed, high density, wet flowing avalanche would have similar destructive power to a large dry avalanche. For a skier, the consequences could be just a bad.

3. "Other than the obvious, are there any mitigating or contributing factors to the likelyhood of a wet slide coming down?"

Radiation balance is the key. Aspect and shape are the keys to radiation balance. Some shapes, such as cirques, bowls, gullies, and other concave forms, tend to produce strong local reflections of shortwave radiation ( + incoming ), while also inhibiting longwave cooling because the shape of the terrain promotes local reabsorption of longwave radiation. Which is a fancy way of saying, some terrain forms are subject to primary shortwave, secondary shortwave, and they don't cool off as quickly.

[jmf]

We had a guy die up here at the basin a couple of years ago in a wet-slide on Pali. The avi guys here are pretty much at the forefront of wet slide forcasting and are still researching historical slide data afaik... Safe to say wet slides are both dangerous and poorly understood.

[Platinum Pete]

I've had a wet slide try to send me over a cliff to rocks below. I had to hang on tight to a tree to keep from being swept over. Before that, we were having a grand old time glissading in the mush and riding the littler slides - blissful ignorance.

[MakersTeleMark]

We had a guy die up here at the basin a couple of years ago in a wet-slide on Pali. The avi guys here are pretty much at the forefront of wet slide forcasting and are still researching historical slide data afaik... Safe to say wet slides are both dangerous and poorly understood.

I would disagree with you in your conclusion that wet slides are poorly understood. Their mechanics and causes are very well understood. Unfortunately, those very same attributes were not recognized as applying to Pali during regular season operation. Big difference.

[TurxSki]

Ha. Ask Spats. He was lucky enough to *only* dislocate his thumb.
Skiing on Kiwi at Mammoth on Saturday (the Mini), he got off course, hit some rotten snow, and it slid out from under him...
He was in the washing machine, got carried over some rocks, lost some gear (recovered), and got injured. He was skiing alone.

I've been "buried" just to the tops of my boots by a wet slide, at Squaw, by tower 10 or 11 of Granite lift.
It's eye opening to feel how you're cemented in there. Easy to go into Panic Mode.

The other thing, in wet stuff, sometimes a big ol' chunk of snow will release above you, where you've made a turn, and this "boulder" will come chasing after you down the hill.
Funny if you notice it coming. A surprise if you don't

[jmf]

I would disagree with you in your conclusion that wet slides are poorly understood. Their mechanics and causes are very well understood. Unfortunately, those very same attributes were not recognized as applying to Pali during regular season operation. Big difference.

I can see what you're saying, but if the conditions were better understood, that slide and subsequent 'suprise slides' in similar conditions might have been more anticipated. Granted, we obviously know more about it now than then, but I'm pretty sure Pali was open for about 50 years without a single wet-slide like that having occurred.

[mogul5480]

Thanks for the beta, guys. Especially the info on radiation balance (never heard that before). I still have to get some more official training before I get out there without the help of some more knowledgeable buddies, but it's always good to get smart.

[spindrift]

This has been floating around...

http://www.adventurefilmworks.com/Videos/May19.mov

Like the guy says, holy schnikies!!!

[tknox]

One thing to pay attention to is the overnight temps before you go out in the spring. A couple nights of good freezes with clear skies will provide a thicker supportable surface crust to ski on (Safer). If it hasn't frozen for a few nights or was mostly cloudy and not that cold the freeze will likely not penetrate the snowpack as far and conditions will deteriorate much quicker.

[TurxSki]

^^^ Good Point!
This is with relatively warm overnight temps, for a few nights...

Kuba sets off down 'Wet-slide alley'

Kuba prepares to pause to survey the carnage

[smitchell333]

I have a report that wet slide conditions are developing in Rocky Mountain National Park. 2nd hand report of someone buried to the waist in a wet slide.

Check out the 5 day Mesowest temperature at Bear Lake. You can see temps have not dipped below freezing at that elevation for several days:

[Core Shot]

https://www.usgs.gov/centers/norock/...anche-research

Wondering with the insanely deep snowpack everywhere if this could be a crazy wet slide spring and summer.

[whipski]

Our old adage was be on top and finished smoking the joint before 9 am