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what makes snow?

post #1 of 14
Thread Starter 
As I sit here watching the rain freeze into a glistening sheet and turn the trees into objects of beauty I wonder why some days it snows, while other days it rains then freezes and still other times hail will fall with terrible noise. What is different about warm wet air hitting the cold air that makes the forms of frozen water?
post #2 of 14

Google search

Since my answer would have been something along the line of "The Snow-pixies did it", here are a couple links found with a quick Google.


post #3 of 14
Thread Starter 
Originally Posted by DrFRAU
"The Snow-pixies did it"
thats good enough for me but if:
"Water changes from the liquid to the solid state when it freezes, creating ice crystals. When this happens in clouds, the ice crystals are in the form of snow."
then they are saying that hail is when water freezes not in a cloud?
Hmmm, not sure I'm buying that explanation...but what do I know.
post #4 of 14
I'm not a weather expert, but I stayed at a holiday inn express last night:

I could be wrong about this, but here's what I think happens:

For snow to happen, small crystals of moisture grow around a particle of something like dust or smoke or pollution. As they circulate around in the atmosphere, the crystals pick up more moisture and grow, then get heavy enough to fall to the ground. The air is fairly dry but cold, so there isn't enough moisure to make big rain drops. The cold air can't hold that much moisture. They pick up their moisture simply by being cold and sucking the moisture out of the air, so they grow in nice neat, six sided patterns.

For hail, there is a lot of turbulent moisture and a wam layer. The moisture probably starts as some sort of snow, but it falls enough to get into warm air and melt, but there is enough of an up draft to keep pulling it back up so that it collects more moisture in the form of rain which as it goes up higher in the atmosphere it freezes. It works like a nasty freeze/thaw cycle This becomes a ball of ice that finally gets too heavy to circulate back up and falls to the ground like a rock. It takes some pretty violent weather to create this, which is why it usually oly happens in the summer during the nastiest t-storms and tornado spawning weather.

Sleet is nothing more than freezing rain. It's created by a temperature inversion in a fairly calm atmosphere, where the moisture falls as rain but freezes on its way down through the colder air.
post #5 of 14
I'm not a weather expert, but I stayed at a holiday inn express last night.:
No I'm not an expert but I saw it on The Weather Channel.
There must be a Cloud particle(dirt,smoke,ect.) for the moisture to attach to. After that it's a dependent on atmospheric conditions and parameters to produce a resultant weather phenomenon. Freezing Rain is a phenomenon that is unique in itself, Micrometeorology. Super-cooled moisture in liquid form is heated by impact friction and then freezes.
post #6 of 14
Snow is what happens when water goes from its gasious state to its solid state without passing through a liquid phase. This process, which is called sublimation (sp?) if my memory serves me right, produces the light airy crystals of a snow flake. Ice is what you get if you freeze liquid water. Hail happens when a frozen rain drop is repeatedly blown up through a thunderhead recieving a new coat of water each cycle.

post #7 of 14
Ydnar, you're right about snowflakes forming from water vapor, but sublimation is the opposite process; ice changing to vapor without going through the liquid phase.
Here's a link to an interesting website about snowflakes:http://www.its.caltech.edu/~atomic/s...als/photos/htm
post #8 of 14
post #9 of 14

Thanks for the correction. It was a long time ago that I learned this and I knew that the word sublimation was involved with the processs of changing states and just wasn't sure how it was used.

post #10 of 14
Actually, I too thought that sublimation was limited to the direction of solid to gaseous states -- but I saw it stated the same way YD did-- somewhere on the net -- I'll have to go see if I can find it
post #11 of 14
Thread Starter 
I should have known there was a science to snow! maybe I'll go back to pixies...they are more fun:-) but this is a good chart!
post #12 of 14
I thought it was clouds and snow guns ?
post #13 of 14
Thread Starter 
Originally Posted by Uncle Louie
I thought it was clouds and snow guns ?
I think you are correct...although my reading indicates that it is not quite that simple.

"Natural snowflakes have six tiny arms, known as dendrites, much like what appears in the background image of this article. Man-made snow, however, forms a compact six-sided structure, allowing it to pack more densely and retain less air. This helps to explain why man-made snow skis more firmly to the touch, and retains its durability more effectively than does natural snow."

It would seem that man-made snow is crystal but comes from spraying water; so I think it must evaporate first and then reform as a crystal? Would that be correct? Otherwise it would just be frozen water pellets.
post #14 of 14
Cool Flake photographs here:


Movie of a snowflake crystal forming

I just wanna know how come CalTech didn't capture any of the pixies in these photos?:
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