What weather conditions are required for it to snow?

Answer 1

Snow begins in the atmosphere as water condenses into a tiny droplet. As more and more water vapor condenses onto its surface, the droplet grows. Cold air then freezes this water into an ice crystal.

Each ice crystal has a unique shape that depends on the surrounding air's temperature and water vapor content. If it is below freezing and there is a lot of water vapor in the air, the crystal grows six evenly spaced branches. More and more water vapor collects on these branches and freezes, making the ice crystal increasingly heavy. Eventually, the ice crystal falls from the sky, leaving the cloud of precipitation that it helped to form. As it falls, the crystal continues to grow by picking up more water vapor.

As it descends, the ice crystal can come into contact with warmer air that makes it melt somewhat. This melting acts like a glue, causing crystals to bond together into larger flakes, forming what many people think of as the "classic" fluffy snowflake. If the crystals melt too much and then refreeze as they get closer to Earth's surface, the precipitation falls as sleet instead of snow.

Once on the ground, snow will remain if temperatures are cold enough to keep it from melting. Glaciers that form on mountains, for example, are made up of snow that accumulates on the ground and eventually turns to ice.
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If you are talking about Man-made snow:

snow cannon (also called snowgun, snow maker or snow fan) is a device used to produce snow artificially. The term artificial snow is mistakenly used for the produced snow; a more accurate term is man-made snow. A snow cannon works by atomizing water with compressed air and allowing it to freeze into snow. The device is often used by ski hills and ski resorts to supplement naturally occurring snow and extend the skiing season. However, for the purposes of skiing, most enthusiasts consider man-made snow to be inferior to naturally occurring snow. This is due to the fact that man-made snow does not form snow flakes like natural snow; instead, man made snow forms crystals that are more dense than natural snowflakes.

A snow cannon usually consists of a high pressure water nozzle onto which a high pressure jet of air is blown. Pressurized water flows from a high pressure hose, which forms small droplets of water. The droplets are then blown on by a high pressure air hose to break them up even farther into tiny droplets (almost a mist). If the surrounding air temperature is near or below freezing, the droplets of water tend to evaporate and rapidly cool. This method only works when the ambient air is at 0°C (32°F) or lower.

If the relative humidity is low (10%), artificial snow can be made when the temperature is as high as 4.5°C (40 °F). This is possible because of the rapid evaporation and evaporative cooling caused by the low humidity. If the wet bulb temperature is below -2°C (28.4°F), snow can be made. There is a direct relationship between relative humidity and air temperature which affects the quality of snow.

The snow cannon was invented by Art Hunt, Dave Richey and Wayne Pierce in 1950.

Answer 2

In short - cold and moisture.

Pretty much all moisture in the atmosphere is the result of evapouration from seas and oceans so the first thing you need is a large body of water where the temperature is above freezing so evapouration can take place.

When the water vapour enters the atmosphere it's carried away by wind and air current and can be carried hundreds or even thousands of miles before falling as rain or snow.

As air cools it loses it's ability to retain moisture and the colder the air the less moisture it can contain. This excess mositure can be deposited as dew or frost but up in the air it's formed into water droplets. If it's cold (sub zero) the water droplets fall as snow, otherwise they fall as rain. On their way down the air usually gets warmer so snow falling from clouds often melts on the way down and lands as rain.

Air cools as it rises so if there's hills or mountains in the way and the air is forced upwards it will cool down and greatly increase the chance of precipitation.

Similarly, if a mass of cold but dry air mixes with a mass or warm and wet air the result can be cool air with too much moisture in it and again the result is precipitation.

Snow is most likely at temperatures close to freezing. Much above freezing and it melts and falls as rain, much below freezing and the air can't retain much moisture. Polar air, although very cold, is also very dry and despite the fact that the Arctic and Antarctic are vast desolate areas of ice it rarely snows here - it's just that when it does snow it doesn't melt. 4km of ice might seem a lot but if it's taken 4 million years to form then it's only 1mm a year.

For more information do a search for the following...
Dew Point
Saturation Vapour Pressure
Temperature Inversion
Leeward and Windward Slopes

Answer 3

It has to be conditions for rain first of all...secondly the temoperature and ground leel has to be no more than 34 degrees. That will allow a cold enough temperature at the altitude of thte clouds to produce snow, which is, after all, just frozen rain.

Answer 4

Under 32 degrees F (0 C) on all levels between the ground, and the height of the clouds.

Answer 5

Moist Atmosphere (high humidity in %)
Temps near or below 0 Celcuis aloft and surface

Answer 6

cold weather dah!

Answer 7

It has to be cold?