Unexplainable - Snow day!

Episode Date: March 11, 2026

Grab some hot cocoa and a warm blanket and let’s talk about the tiny crystals that fall from the sky. Guest: Jessica Lundquist, professor of civil & environmental engineering at the University of Washington For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠[e-mail]⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

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free of charge. BetMGM operates pursuant to an operating agreement with Eye Gaming Ontario. All right. It is a day after a very intense snowstorm here in New York City. And my editor, Joanna, came up with the idea that I should go outside and talk to people about the snow. So I am looking out at what can only be described as a winter wonderland. Everything is truly covered. It's like not a blanket.

This is it. It's covered in a quilt of snow. It's like fluffy and white and charming and cold. I don't want to go outside. Oh, it's so windy. Do you hear that? All right, let's go. A few weeks ago, I had an extremely nice time wandering around the streets of Brooklyn in Prospect Park and talking to people about the snow. I can say this park, it's beautiful. It has a lot of trees. and all of the trees are really snowy. I can see a lot of snowmen. There's a huge snowman over there. Like, I don't know how to say it in feet,

but I can say it's at least 160 centimeters. We realized this morning that this was the best snowman-making snow that I've ever seen. And so we made this snowman this morning. Now we're back to give it a personality. Is that about sum it up? Help. Help what?

You're about to slip? Well, we already built a snowman, and we froliced in the park. So now we're going to go get some hot cocoa. I talked to people who were shoveling their walkways, going sledding, going skiing. I am wearing my cross-country skis from high school. How are you fitting cost-country skis in your New York apartment? It's a great question. I talked to people with lots of thoughts on snow.

I love working out. I love shoveling it. I cross-country ski. I just love it. Pro snow. Love it. Except a month from now, we still have it, and it's black. Yeah, like once it gets disgusting like the last snow did, then I'm over it.

But I like this snow for right now. I love it from a distance. Only because he's small, we out here other than that, I'd have been in my house. But I do love it from a distance, though. And I also ask people if they had questions about snow. Well, I know that it makes things very quiet because it absorbs sound. But I don't understand. I guess I don't know the science.

behind why? I did it here. I'm not sure if it's true that like every snowflick is different. I guess one question would be sometimes when snowfalls, like you can't really make snowballs out of it. And then sometimes it's perfect like this

where you can, you know, you can grab it and make a snowball. Yeah, just kind of what determines that because this feels like a totally different ballgame. So not everyone had questions for me. Not really. I kind of like not knowing. Like not knowing how things...

The magic. Yeah, you know what I mean? Okay, great, I'll go home. That's not what I did get enough questions that I decided to call up a snow scientist in search of some answers. So I am Bird Pinkerton, and today on the show, I'm talking to Jessica Lundquist. She's a professor of civil and environmental engineering, and she's going to answer a whole bunch of questions about snow for us. Of course, this is unexplainable, though. So a little later in the show, she's also going to tell us some things about snow that she does not yet know and is still trying to figure out.

A bunch of questions for you as our resident snow expert, I guess. So the first question I got from a few people is actually about the shape of snowflakes. How was it formed? How does design come about? Like, is there anything that makes it have a different shape, the snowflake? Why are snowflakes all different shapes? So snowflakes will form around a tiny speck of dust, called a condensation nuclei. Okay. But now it can grow in different ways.

So you can grow out to make what we call a dendrite shape. So that's your postcard snowflake. But it could also grow down, right? So you could also get a column. Which one of these you get will depend actually on the temperature and water vapor content in the atmosphere where the snowflake is being formed. Depending on the conditions in the atmosphere, it will grow in a certain way. And then it's not sitting at just one point in the atmosphere.

It's often being blown up and down to different points with different amounts of water vapor, different temperatures. And so it's often like growing differently throughout its lifetime. And then it has to fall from that cloud down to where we are at the surface. And it will often like hit different snowflakes and then they can aggregate and you can get these sort of messy big things. Wait, so what you're saying to me is like the snowflakes shape is like a record of the life it's lived almost, like where it's been? Yes, so it's telling you about where it's been in the cloud and what it's fallen through and whether it hit another snowflake and how it grew.

And if you really want to know about snowflakes, I recommend checking out Ken Liebrick, who grows them in his lab at Caltech. He can make designer snowflakes. Every day I learn about a job that I wish I had. Okay, so the answer to this first question of sort of like, why is every snowflake different is like every snowplake has its own little individual path through the atmosphere that shapes how it grows. And then also go check out this guy's designer snowflake lab. Yes. Question two is I got a question kind of about. not how it looks, but how it sounds.

So one of the people I met did sort of like an ASMR demonstration of the snow crunching. And then was asking, like, why does it crunch like that? So we talked about the snow snowflakes history in the atmosphere, right? But then the snow also falls on the ground and has a history on the ground. So your snowflakes start accumulating on the ground and you have all these, you know, little individual snowflakes that fall on top of each other. and they have air in between them. It's not ice. It's a pile of little snow crystals with air in between it.

Like a fluffy pillow almost, the way that your pillow is like a bunch of feathers. Except this is cooler than feathers because snow is always close to its melting point. So if you think about some material science, if you have like metal and you heat it up so you can weld it and center it, if you get your metal really close to its melting point, you can like make two points of metal actually attached to each other. So snowflakes will do something we call sintering. So you also center things with metal, but snow will center by itself just sitting there. So your snowflakes fell down. They made, you know, kind of like your feather pillow with air inside. And then your little crystals start attaching themselves to each other. So now you have this

matrix of snowflakes that are attached to each other. And then underneath it, they have air. You could also have right at the surface, it might melt and refreeze a little bit. So they'll often be, you know, attached at the surface with air underneath. Now, your crunchy sound is you're breaking that. Oh, you're breaking the connections that they formed. Yeah. But it's only sometimes. Your snow won't always make a crunchy noise, okay? So basically, like, because snow is slightly melted almost, but it has the power to stick together, it's forming all these sort of fragile bridges. Yes. And when you crunch it, you're just demolishing a lot of bridges. all at the same time.

Great. Another sound question. This is question three. Why does snow absorb sound? Okay, and this, it doesn't always do that either. So one thing is snow flakes are all different. The snow on the ground is also all different. So sometimes it might make a crunching sound and sometimes it might absorb sound.

So when it most absorbed sound is right after new snowfall. So it hasn't yet had time to make all these centering connections. You just have a whole bunch of little snowflakes, just lose. Lusely lying at surface. So think of kind of like your feather pillow, not yet attached, but lots of air in between it. So the sound gets kind of muffled by going into all those air pockets in the snow and doesn't get reflected back to your ear. So it ends up sort of being a sound absorber because it's just loosely connected a whole bunch of air pockets.

Delightful. Okay. So then I got a lot of questions about why the snow is the way that it is. So people were talking about sort of like the texture of the snow in this storm versus the one two weeks ago. It seems like thicker and stickier. And like the fluffiness, what makes it so fluffy? One person got really descriptive. It's like AI snow.

What do you mean? Like I feel like it was 3D printed. It's like temperate snow. But it's apparently like better for snowballs, better for snowbuilding. Yes. And people wanted to know like. what was going on there essentially, like physically, chemically, whatever, to make different snows after different storms?

Yes. So, again, we talked about the history, right? It starts with they're falling through the atmosphere. They fell through different atmospheres, warmer storms, cooler storms, depending on the conditions in the atmosphere, snow crystals grow differently, and they also have different amounts of liquid water inside of them. So if you get a colder storm, you have a lot less liquid water. and you end up with you dry snow. It won't make a snowball, right? So as you get warmer and you get

the biggest change above negative three degrees C, so as you get between, again, when we talked about snow being really close to its melting point, right? So snow is melting points at about zero degrees C. And as you get really close to that, you actually get more molecules that actually are liquid. And that makes it really sticky. You can build good snowballs with warmer snow. One person asked how it accumulates on surfaces. And so specifically, we were talking about tree branches. And then I was thinking about wires. And I was curious if there's any interesting physics or whatever going on structurally there.

So there are actually these amazing studies done both in Japan and in Switzerland, where they put out all these boards of different widths and different sizes. And then they just measured how much snow accumulated on all of them. The pictures in their papers are really cool. What? And they also did studies where they tried to see, like, how tall could you stack snow and, like, what was the angle of repose of just a stack of snow? So these are questions that lots of people have. Maybe not lots of people, but it definitely been studied quite a bit. It goes back to some of the things we talked about before.

So how much snow you can stack up actually depends on the temperature of the snow. So again, we got back to that snow being really close to its melting point, particularly if you have a warmer snow. right? And the fact that the snowflakes can center and stick to each other. So they will actually attach themselves to each other. Also, the stickiness per se of snow goes up hugely between negative 3 degree C and 0 degree C. If you think about little bits of it will like melt and be liquid and then refreeze again, that it will sort of freeze itself onto your tree branches and your different things. And then it will attach itself by centering to each other. And so it's can stack up amazingly.

Oh, okay. I'm learning a lot. Unrelated to structure of things, one person asked what the benefits of snow are for the environment, so like for trees or for parks, etc. Snow insulates things really well. Just like in your house, the insulation is, you know, a lot of pockets of air in between two walls, right?

Your snow builds up with a lot of trapped pockets of air. that insulate the temperature. So it turns out that in most cold regions, the temperature at the top of the snowpack above the snow is significantly colder than the temperature at the base of the snow. So if you go to the Arctic, it's often like more than 20 degrees Celsius different

between the top and the bottom of the snow. So it'll be, you know, like can get negative 40 in the air. And if you're under the snow, you're super warm. So if you're out in a really cold storm, you could dig yourself a snow fort. bury yourself under the snow, you'll be warmer, right? So a lot of animals live under the snow, some hibernate under the snow, many build their dens under the snow, right? It's a warm, safe place through the winter.

And is it just animals, or are there other things kind of taking advantage of this warm blanket effect? Plants, microbes, you know, things in the soil that are using that same insulation to survive, like plants with shallow roots in cold regions will often have root damage if there's not a good snow year. It's kind of counterintuitive that often in years with less snow, it's colder for a lot of plants and animals because they can't hide under that blanket. So, clearly there is a lot about snow that's no mystery to Jessica. But there are some things Jessica does not know about snow. So after the break, it's snow mysteries. with Jessica.

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From binge all episodes exclusively on Paramount Plus. This episode is brought to you by Defender. With its 626 horsepower twin turbo V8 engine, the Defender Octa is taking on the Dakar rally. The ultimate off-road challenge. Learn more at landrover.ca. Jessica Lundquist was patiently answering all our questions about snow. But I also had some questions about Jessica, like what got her into studying snow to begin with?

She told me she grew up in California, and her favorite thing to do was to go to Yosemite. I just liked going in the mountains and going hiking, and they went in the summer, which generally there's no snow. But then quickly realized that the amount of water in the river that I like to jump in and go swimming was completely related to the amount of snow in the mountains. So you were like, I'm going to spend a great deal of my career studying this question? No, of course not. I said I want to be a park ranger and just go hiking in the mountains. She did wind up becoming a researcher, though, not a park ranger. And she began tackling this big question related to snow.

How much snow is there actually in the mountains? It turns out that on the west coast of the U.S., snowmelt can be an important source of water. So basically, in the western U.S., we don't have enough water for all the things we want to use water for. There's a lot of people living in the West. There's a lot of crops grown in the West. All of these need water to grow. And basically, the water is allocated to people for this water right system. So in terms of like what is the value of snow, it's like free reservoirs, right?

It's storing that water in the winter for the summer. So people always want to know how much water exactly do we have in a snowpack? because it's actually so dry out here that people will be told don't plant, right? We can't give you water this year. You can't plant your crops. You need to furlough your fields. You need to do something else.

So a lot of what I try to do is figure out how much snow there is in the mountains at any given point in time. I mean, the job is often to predict the future, right? Can you predict how much water we'll have in the future? But this is easier said than done because it's tricky to measure how much snow there is in the mountains.

A lot of snow falls in places that don't have roads, that don't have infrastructure. They're rugged steep terrain without, you know, a lot of access. So a lot of it fell a place you can't go. But it also, like, it's extremely variable. So if you put out a measurement site, so the National Resource Conservation Service, or NRCS, has something that's called a snow pillow. Okay. So it's basically, you have, like, two metal plates, you fill it with antifreeze,

you put it right by the surface of the ground, do you bury it slightly, so bears can't find it. The snow falls on it, squeezes the water in the antifreeze, which then creates a pressure gradient, and it tells you how much, what is the weight of the snow resting on this snow pillow? So basically that weight tells you what we call the snow water equivalent. Like for basically, for water resources, if all that snow melts, how much water do we get out of it? This is the snow water equivalent.

We may heard the term SWE, snow water equivalent. I have not heard the term sweet, but I have not heard the term sweet, but I, like the term sui quite a bit. Okay. That sounds great. That sounds like we have a measurement. Fantastic. Exactly.

But if you walk 10 steps to the left, you're going to measure something completely different. Oh, right. Okay. This is somewhat less sweet. The same problem exists for other measurements, and satellite images can be tricky. And so Jessica and researchers like her may never be able to work out at a perfect measurement. of the snow in the mountains on any given year. What they can work out, though, is patterns.

So for many decades now, people have been taking measurements of snow in the mountains at certain spots, and then seeing how much water there ends up being in the following warm season. And that means that they can say, you know, when our measurements look like this in these various spots, there will probably be this amount of water. Emphasis on probably, though, because the predictions are not always as neat and tidy as this makes it sound. So that's why I'm still employed. So the number of things can trip people up. One thing we did recently, so basically Colorado, Colorado River provides water for what seven different states who all argue about much water they get is often in the news, it's not having enough water.

And what they've noticed is since 2000, the amount of water in the river was less. than what the snow predicted. And 2021 was a particularly bad year. They thought from the snowpack, it was kind of close to average, and then it delivered way less streamflow than they thought. And so, you know, then people aren't prepared because they bought their seeds to plant, and then they get the water cut off and they lose their crops.

And so it's for some people, economic disaster, to get this forecast wrong. Jessica says the reason these forecasts were wrong was that it had stopped raining as much in the spring, in Colorado. And so if it is super dry and warm in the spring after April, after they take that survey, it turns out that the plants wake up early and it's sunny. And they say, okay, I'm going to start using water to grow as a plant. They start transpiring, evaporating. And a lot of that water goes back to the atmosphere instead of in the stream. So the plants before it can even get to the

stream, the plants near the snow are like vacuuming it up in a variety of ways. Yeah. Is climate change affecting your predictions at all? So basically, climate change, warmer temperatures, the biggest impact is that more precipitation falls as rain instead of snow. So now, in terms of predictability, rain is fast, right? When it rains, it runs off right away. So the snowpack, what it does is, like, it actually allows us, at this time of year and

traditional April 1st snow surveys to say, this is how much water is going to be in the rivers in the summer. We actually have no idea how much it's going to rain in May or June in the Western U.S. right now. Like that we can't forecast, right? And without the snow, it's that kind of guess of how much will it rain in the future that we have to rely on. So snow itself, by virtue of just storm.

pouring the water on the hillside gives you a lot of predictability that we don't have when it falls as rain instead of snow. Fascinating. All right, easy question to end. Is there a snow that you would revisit from your life that you'd encountered? Yes. So I did a project. We were studying snow out in Gothic, Colorado, which is sort of by Crested Butte, middle and nowhere, Colorado Rockies. We are staying in this old abandoned mining town that is now a biological research station that you can only access by skiing in. So we've skied in and we're staying in this old mining town. And every day we are cross-country skiing out to our measurement sites to dig in the snow and measure things.

And so we're the only people out there and it's like snowing really lightly. And I was the front of the line of everybody heading out just sort of cross-goats through. skiing on our route. And then all of a sudden, right in front of me, I disturbed a bunch of tarmigan that were hiding under the snow. So the tarmigan, especially when it's really light, fluffy snow, they will, like, bury themselves in the snow. But as I went by them, I scared them. So all of a sudden, the snow erupted, and a whole flock of white birds flew out of the snow right in front of me. And all around me, it was like the snow erupted birds. I mean, it was beautiful.

That's so magic. I keep looking online. Like, hasn't someone videotaped this? I can't find a, like, YouTube recording of, like, Tarmigan erupting from snow. If you ever find one, you have to send me. Okay, this is perfect. We had, we brought, we came to you with questions that people had,

and now you are leaving our audience with a question that you have, which is, does anyone have videos of, A bunch of parmigants. Of tarmigants. Well, I'll let you know if anyone sends us any. Thank you. If you want to read more about Jessica Lundquist's research, you can find her at the University of Washington's Department of Civil and Environmental Engineering. This episode was produced by me, Bird Pinkerton.

It was edited by Joanna Solitarev. It was also her idea to send me walking through the cold and snow. This one lovely person I spoke to put it. Do some of this. I'll let her know. Christian Ayala did the mixing and the sound design. Noam Hassanfeld does our music. Melissa Hirsch checks our facts.

Jorge Just, Meredith Hodnott, Julia Longoria, Sally Helm and Amy Padula are the fact that some macaques in Japan have been recorded making balls of snow that they roll down hills. Thanks so much to everyone who gave me their questions and their thoughts on snow.

I really appreciate you all. And if you have videos of Tarmigan, bursting from snow, please send them to Unexplainable at Vox.com. If you have videos of any birds bursting from snow, honestly, or animals bursting from snow, send those along to Unexplainable atVox.com, too, please. Also, I had a ton of fun producing this episode, like sort of an irrational amount, and I was thinking I might do another episode about snakes. So if you have snake-related questions, please record a voice memo and send it to us.

No question is too silly. Just tell us your name, your age, your question about snakes, and we might use it on the show. We are, in case you missed it, unexplainable at vox.com. If you would like to support the show and the journalism the Vox does, we would love it if you would become a member. It is very easy to do. Just go to Vox.com slash members. you'll get access to all of Vox's journalism, but you'll also know that you were supporting Vox's journalism.

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