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In a story I am working on, I need a scene in which one of the main characters finds himself outside in precarious weather conditions, unable to see unaided much farther out than an armlength or so.

For the purposes of this question the setting is essentially our Earth, and my draft geographical location (which isn't vitally important; I can fairly easily change this if it's easier to make it work somewhere else, as there aren't many outdoors-settings-sensitive scenes and much of what I've done is in a sort of prototyping stage anyway) is somewhere in the far northern or northeastern parts of Canada. The time of year is tentatively mid-February, which means temperatures in the range -30 to -35 °C are not at all unreasonable and anywhere down to about -45 °C might well be plausible if there is a bit of a cold spell. At the time and place I have in mind currently the sun is just around the horizon.

I've been considering having Our Hero outside at a time when the weather shifts from quite decent (just cold) to strong wind with heavy snowfall (basically a white-out), possibly coupled with a fog to further reduce visibility.

  • Is a (preferably quickly developing or approaching, but I'll take what I can get) fog realistic at those temperatures? Is there any particular setting element, or earlier weather, which would increase or decrease the realism of that? (Presence or absence of bodies of water, lowland/highland/flatland/mountainous region, recent shift in weather conditions, ...)
  • Is combining a fog with a snowstorm (or at least strong wind, which can be put into service to whirl up snow on the ground from recent snowfall) realistic? Again, is there anything in particular which can affect the realism of it?

Bonus question:

  • Are there any particular, probable effects of those conditions on soon-to-follow weather which I should take into consideration for the following scenes for the depiction to be as realistic as is reasonably possible?

What I want is the situation described at the top. Answers which address how to put the character in such a situation, if they explain why my idea won't work, are also welcome.

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    $\begingroup$ You can mix fog and hail...but that hurts a lot more than snow... $\endgroup$ – James Oct 2 '14 at 20:05
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    $\begingroup$ You really don't need to add the fog. A White-out snowstorm can be dense enough to render a person nearly blind- you cannot see beyond 3 feet away. $\endgroup$ – VolleyJosh Oct 2 '14 at 22:50
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My answer is yes, you get fog in these conditions. Might not be traditional fog, but it's an icy haze that resembles fog and tends to leave ice crystals everywhere. You need an open water source (rivers usually...the center of them never fully freeze) and then an intenser cold front to wander through. The open water provides heat and water vapour, while the incoming cold turns it to an icy fog. It might not be the same type of 'fog', but it sure looks like it.

Is a (preferably quickly developing or approaching, but I'll take what I can get) fog realistic at those temperatures? Is there any particular setting element, or earlier weather, which would increase or decrease the realism of that? (Presence or absence of bodies of water, lowland/highland/flatland/mountainous region, recent shift in weather conditions, ...)

Yes. In between the mass of cold arctic air from the north and the warmer wetter air to the south, you get a jetstream (high wind area). this jetstream can fluctuate north and south relatively rapidly and shift temperatures from warm and wet to cold and dry in a matter of a few minutes (In Calgary Canada, there's the general saying...if you don't like the weather, wait 5 minutes...I've personally seen 10 degrees and relatively nice, to -20 and cold as **** and then back to +15 in a matter of an hour. Look up 'Chinook' if you want the local term for it). This rapid shift can lead to quick fogging around the river. I think the body of water presence is definitely required...the position of Calgary beside the mountains and plains tends to see higher winds which bring in the shift from cold to warm faster.

So yes to the decent cold to full on blizzard in a very short time frame too.

Is combining a fog with a snowstorm (or at least strong wind, which can be put into service to whirl up snow on the ground from recent snowfall) realistic? Again, is there anything in particular which can affect the realism of it?

Not sure here...the fogging effect usually requires much more still air, otherwise it dissipates faster than it's formed. Admittedly, in a full white out snow storm it'd be tough to make out if there is fog or not ;) Snow storms tend to be large weather fronts that hit a larger area, while ice-fog is a generally a localized effect. I can see the switch from icefog (still air) to a massive blizzard...but I have more difficulties seeing a massive snowstorm followed up by fog.

Honestly a blizzard being near white-out and having fog to 'further obscure visibility' is kinda like putting on a blindfold and then turning out the lights...blindfold (the white-out) is far more inhibiting than turning the lights out (fog).

Remember that light plays a big role in this. It is a 'whiteout'...even fully obscured by snow, there is actually quite a bit of light hitting everything as it reflects from snow flak to snowflake. It can be quite bright if you're in it during the middle of the day.

Are there any particular, probable effects of those conditions on soon-to-follow weather which I should take into consideration for the following scenes for the depiction to be as realistic as is reasonably possible?

very often the storm front moves to the south, leaving behind a high pressure arctic system...cold and very clear air with little clouds. This leaves you with everything covered in a very reflective environment (white snow reflects almost all light) and a clear day with plenty of sunlight (snow-blindness becomes an issue here). If the wind dies down, the result tends to be overtly large and soft snowflakes fluttering around.

And a final note - of particular nastiness when in a blizzard is the wind can and will freeze your eyes. The natural defence of course is to squint, but the hard winds will also cause your eyes to water. Watery eyes plus squinting can result in frozen eyelashes that refuse to open beyond a squint.

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    $\begingroup$ You don't really need an open water source -- it forms around here even well after the river freezes completely over. It certainly helps, because it contributes to the humidity necessary, but it's not an essential component. Excellent point about your eyelashes freezing together, though it's worth mentioning that it's trivially easy to thaw them or brush away the ice -- though they do tend to freeze back together right quick. $\endgroup$ – Kromey Oct 3 '14 at 0:43
  • $\begingroup$ I completely agree with Kromey, we do get some foggy days in the middle of the winter in Regina when all water is frozen. $\endgroup$ – Martin Argerami Oct 3 '14 at 13:18
  • $\begingroup$ Ah true, I guess the fog I see is mostly from the water anyway...you still need that bit of warmth to get the initial humidity in the air, open water is just the convenient version of that. Even in the -20 and -30, there's alway a minimal trickle down the center of the river where it doesn't quite freeze (unless it's prolonged -20s). And yes, trivial to thaw eye lashes, but you have to expose fingers to do so. $\endgroup$ – Twelfth Oct 3 '14 at 16:23
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Contrary to the previous answers, as someone who actually lives in these climes, I can tell you that yes, absolutely, you can have fog at these temperatures.

It is not, however, your "typical" fog -- around here we call it "ice fog"1, because it is literally tiny ice crystals that have formed around microscopic particulates in the air (water being capable in the conditions around here of actually being liquid down to -40C/F), but the effect is the same and any reasonable observer looking at it (and not thinking about just how gorram cold -40F/C actually is) would reasonably conclude that it is fog. Those of us who live around here quite frequently just call it "fog", in fact.

So there's two possibilities for your character:

  • He's not a local, in which case it looks and acts just like fog and he'd reasonably call it "fog".
  • He is a local, and knows full well what it actually is, but just like the locals used to the stuff he reasonably calls it "fog".

An interesting feature of ice fog is that it leaves a fine dusting of "dirty" ice crystals on absolutely every exposed surface, whether horizontal or vertical. Not really noticeable on snow-covered ground, of course, but you'd see it on buildings and streets (where, incidentally, it makes them quite slick!).

Your best bet to get an ice fog is to drop the temp rather rapidly from "warm" (that is, somewhere around -10 to -20F/-20 to -30C) to "absolutely frigid" -- a drop of around 20 degrees F (about 10 degrees C) will do it quite easily. You have to have around 100% humidity (or darn close), but keep in mind that that means "100% of the humidity air this cold can hold", which is a heckuva lot drier than, say, 10% humidity in a Texas Gulf Coast spring. Pollution helps (it adds particulates, though it doesn't have to be anywhere near San Francisco smog-levels), but is not required.

That's not the only way, you can go to bed one day at -40F/C and wake up the next morning to pea soup ice fog and it's still the same -40F/C. Weather's crazy like that. That's just your easiest route to ice fog, but really you can have almost any weather you want and you can realistically get it. Of note however is that it cannot form below -40F/C, nor will it form if you've just warmed up past that point (and, really, it's exceedingly rare to see it when temps are climbing anyway -- it almost exclusive forms when they fall). It can stick around if it forms and then the temps drop below that point, of course, but the ice crystals will begin sublimating and it won't last long.

That said, a strong wind would most likely simply blow it away -- being floating ice crystals rather than proper moisture, it seems far more susceptible to wind. (That's merely my subjective observations of literally 30+ years living with this stuff.) However, you absolutely do not need it -- when you have driving winds whipping snow up off the ground as well as fresh snow falling from the sky ("whiteout"), you can't see your own hand in front of your face. It's not merely that there's so much snow in the air whipping around you, but also that that icy wind driving into your face provokes a reflex reaction to close your eyes, and you can barely open them enough to squint. (Wearing ski goggles helps, but unless you're actually skiing no one -- not even those of us who regularly encounter these types of conditions -- carries those around.)

It's worth noting that it's not merely the snow itself blocking your vision -- what light gets through the clouds and snow reflects chaotically off of the flying snow, blinding you. "Snow blindness" is a common side effect of being in whiteout conditions if one's not prepared (i.e. wear your sunglasses!), and it doesn't even have to be particularly "bright" as you see it -- UV light is quite adept at punching through clouds and snow, and more than capable of blinding you!


1 There is another, more "technical" term for "ice fog", but it escapes me at the moment. And no, I don't mean "pogonip" that Wikipedia mentions -- I've never heard that term. No matter, no one but meteorologists use it anyway, and not even when reporting the weather on the local news.

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    $\begingroup$ The other bonus for the OP is that torches area an absolute nightmare because they simply reflect off the fog making the situation worse! $\endgroup$ – Liath Oct 3 '14 at 9:52
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No, fog can not be combined with a snowstorm.

Fog is a result of water evaporating and then becoming minuscule liquid particles again, floating in the air, which is very difficult at low temperatures, and can not happen under 0C. At these temperatures, liquid water solidifies and, in turn, can sublimate, but there will not be liquid water floating in the air (which is what fog is).

Instead, you can have a good amount of snow dust (solid water, instead of liquid) floating in the air. The effect is the same, but you just use the correct state for the water.

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    $\begingroup$ Disagree pretty strongly with this...as someone who has lived in northern Canada who gets to experience this frequently in winter months...you get a good amount of fog created around open water (rivers that haven't frozen over completely, usually occurs when there is a sharp temperature dip from an arctic front moving over, which is also when the heavy storms occur). The warmer flowing water creates the water vapour needed which turns into an ice crystal fog. $\endgroup$ – Twelfth Oct 2 '14 at 21:05
  • $\begingroup$ @Twelfth user said "-30C to -35C". I can not think on flowing rivers at these temperatures, nor any other open waters. $\endgroup$ – Envite Oct 3 '14 at 7:20
  • $\begingroup$ @Envite: I walk to work in -30 to -35 weather every winter, and sometimes it is indeed foggy, even though there is no flowing water. $\endgroup$ – Martin Argerami Oct 3 '14 at 13:15
  • $\begingroup$ @Envite - You cannot think of it, yet many live it. I'll send pics this Feb if you'd like...stuff like : fotosearch.com/CSP295/k17484044 the center of a large river rarely freezes, even in -20 conditions. In a few stock photos I found with a simple search, you can actually see the fog rising off the center of the river where it's still flowing. $\endgroup$ – Twelfth Oct 3 '14 at 16:35
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In my experience, no. Fog doesn't work with cold, at least not that cold. When you are getting to those temperatures your breath crystallizes a few inches from your mouth. You can feel the cold trying to freeze your lungs. a brisk walk down a hill and you need to blink frequently to keep your eyes from freezing. Those temps would squeeze the moisture out of the air and could make one hell of a snow storm if it came up fast.

I've been in snow storms were you really couldn't see more than a few yards and when the wind is really blowing it's hard even to keep your eyes open.

I was in a XC ski race at -40, one of the racers had to go the hospital because of frozen eyeballs. I'm assuming just the corneas but never heard the specifics.

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  • $\begingroup$ At -40, fog is more common than snow, at least where I live. $\endgroup$ – Martin Argerami Oct 3 '14 at 13:20
  • $\begingroup$ yes, much below -30 and it's usually too cold to snow. $\endgroup$ – bowlturner Oct 3 '14 at 13:21
  • $\begingroup$ But not too cold for fog. $\endgroup$ – Martin Argerami Oct 3 '14 at 13:23
  • $\begingroup$ if you count suspended ice as fog. The question was about fog and an snowstorm white-out The two are separate phenomena. The 'fog' is in quite still days, the storm has wind $\endgroup$ – bowlturner Oct 3 '14 at 13:25

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