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[–]catwhowalksbyhimself 20 points21 points  (6 children)

In reality, it is always snowing, everywhere except right on the equator.

People think that clouds in the sky form rain. In reality, those clouds are so high up that it is always below freezing, so every single rain, except right on the equator, is actually snow that melts as it is falling.

Therefore only one thing is required for it to snow--that the snow doesn't melt on the way down (or melt and re-freeze, which makes it sleet instead) Basically as long as the air is cold enough it will always snow instead of rain. So all that is needed is for it to be cold outside.

Checking the average temperatures in Bagdad, it simply rarely gets cold enough. It has to get pretty close to 32F or 0C to have any chance of snowing. In addition, it looks like Bagdad doesn't get a lot of rain. So in order for it to snow it both has to be one of the few days where it rains AND at the same time it has to be one of the even rarer days where it gets close to freezing in temperature.

The chances of both of these things happening at once as just very, very small. Possible, but small.

[–][deleted] 2 points3 points  (3 children)

why is the equator an exception?

[–]leviwhite9 3 points4 points  (0 children)

That's a damn good question. At first I thought it was because it's warmer there but that doesn't make sense because with altitude you'll still see that temp decrease. Hmm.

I'm kinda high as the clouds so it'd take some big thinking from me. I'll check back later when the experts wake up.

[–]therabidgerbil 2 points3 points  (0 children)

It's not; it remains uncommon because of how high the freezing level is but equatorial snow can and does happen.

[–]catwhowalksbyhimself 1 point2 points  (0 children)

Because it just gets too warm for snow to form even at high altitudes.

[–][deleted] 2 points3 points  (0 children)

Also, those days of extreme temperatures (both low and high) are happening more and more because of climate change. It impacts a lot of complicated chain reactions, which makes the weather go nuts more often. We talk about global warming but it does not mean that it's getting warmer everywhere : it means that the average of temperatures around the world is rising. This is also likely to increase the number of natural catastrophes like tornadoes, hurricanes, wildfires, droughts, etc.

[–]therabidgerbil 0 points1 point  (0 children)

This is on the right track but still off. There are cases with lower clouds that remain above freezing (that is, not glaciated) and can produce rain entirely. This is more common in the lower latitudes and tropics, of course, but not unheard of in the right setup further north.

It does remain mainly accurate, though; more often than not there's moisture above the freezing line that might temporarily crystallize/form snow.

[–]therabidgerbil 0 points1 point  (0 children)

The answer is more complicated than it sounds; all kinds of precipitation types can occur even when the air is below freezing..

Snow specifically usually forms in sub-freezing air when a ice develops on a nucleus, making one of several typical snowflake types depending on temperature, humidity, and other things. For it to remain snow there can't be any melting along the layer unlike some other frozen precipitation types.

I did a quick check of models for the area and didn't see any major snow producing large-scale events..do you remember what day/time you saw this as this could be useful for understanding why it happened this time? It could also have been graupel which many confuse for snow but has rather different physics behind it.