I remember hearing since I was young that snow was most likely the temperature was right around 0 Celsius, 32 Fahrenheit. Ok, I know that as the temperature gets colder, the air can hold less moisture. And precipitation requires moisture in the air, right?
So is there a correlation with temperatures right at freezing and the amount of snowfall?
When does altitude come into play? With a given temperature and moisture level, is there more snow at high altitudes than sea level?
It is true that, as air gets colder, it can hold less moisture. Snow that falls right around freezing tends to be “heavy” in the sense that it is very wet snow (the type that’s good for making snowballs and snowmen). But, such snow also tends to compact quickly, and may even start to melt soon after falling, depending on how warm the ground beneath it is.
OTOH, if it’s a bit colder than 32, the snow that falls tends to be lighter in texture and fluffier, and this is often the type of snow that yields impressive snowfall totals.
If it gets really cold (well below zero F), the air can hold very little moisture, and it’s unlikely to snow a lot, but it’s still possible to get snowfall.
Also in clear weather, the night time temperature falls quite fast since there are no clouds to reflect the infra-red coming from the ground and thus we tend to associate cold and clear.
Weather forecasters talk about the snow to liquid ratio which is based on temperature and moisture variations in height of the air column in which the snow will be generated and the type of crystals that form and how they fall. As a general rule, the ratio is usually around 10:1 which means that if you take 10" of snow and melt it then you’d get 1" of water. Heavy wet snow like you’d get when the temperature is right around freezing may only be 5:1, but in colder weather well below freezing like around 15F (-9C) you can get much fluffier snow at more like a 20:1 ratio. So that being the case, colder temperatures would seem to lead to heavier snowfall, but then there’s the counteracting force of colder air having less moisture capacity.
The trick with big storm systems is that they bring in a ton of moisture and thus warmth. By the time you get to the below-freezing side of the storm, a lot of the moisture has already been wrung out as rain. Try to push that moisture farther to the cold side and you’re more likely to just shift that rain/snow line farther with it, so you just get more rain. So it’s not just about the straight up temperature but also the dynamics of winter storm systems too. One to two degrees can mean the difference between an unremarkable cold rain and a major snowstorm.
A little quick Googling didn’t yield a Goldilocks temperature for snow, but it might be around 20F (-7C). That’s cold enough for a high snow to liquid ratio, due to different types of crystals that form at that temperature compared to when it’s warmer. However it’s still warm enough for good moisture capacity. This needs some more research.
So my confusion…
“Temperature” as recorded is ground temperature. Snow forms up much higher.
Winter does weird things to the temperature gradient going up doesn’t it? Cold air coming in running under warmer air, snow’s albedo, both cause inversions, so column can go cold warmer colder up higher. Or might not.
So how much do ground temperatures correlate with the temperature of where the snow forms and what it needs to drop through? I can find something on line about inversions causing freezing rain but not much else.