snow cannon: Information and Much More from Answers.com

A snow cannon (also called snowgun, snow maker or snow fan) is a device used to producesnow artificially. The term artificial snow is mistakenly used for the produced snow; a moreaccurate term is man-made snow. A snow cannon works byatomizingwater and allowing it tofreeze into snow. The deviceis often used by ski hills andski resorts to supplement naturally occurring snow and extendtheskiing season. However, for the purposes of skiing, most enthusiasts consider man-made snowto be inferior to naturally occurring snow. This is due to the fact that man-made snow does not form snow flakes like naturalsnow; instead, man made snow forms crystals that are more dense than natural snowflakes.
Snow cannon constructors have been following these aims:
to maximize the amount of snow made,
to extend the period in which snow can be made,
to minimize the amount of energy needed,
to minimize the impact on the environment.
Withglobal warmingthe ability of snow cannons to function in high temperatures hasbecome very important, but it should be noted that their high usage ofboth water and power are also increasing this effect.Annually, Europe‘s 3100 snow cannons alone use as much energy as a cityof 150,000 inhabitants and about the same amount of wateras 1.5 million people in a city like Hamburg.
Homemade snow cannons are gaining in popularity.
Construction details

Rear view of snow cannon at Mölltaler Gletscher,Austria,showing the powerful fan.
There are two main styles of makers: a snow gun and a snow fan. A snow gun is very tall and uses higher pressure water, whilea snow fan uses a powerful axial fan to propel the water jet to great distance.
A modern snow fan usually consists of one or more rings ofnozzles which turn high pressurizedwater with snomax, witch is made from bacteria, into small droplets. A further ring of nozzles is fed with a mix of water andcompressed air and produces tiny crystals of ice. The small droplets of water and thetiny ice crystals are then mixed and propelled out by a powerfulfan, after which theyfurther cool through evaporation in the surrounding air when they fall to the ground. The crystals of ice act asseeds to make the water droplets freeze at 0°C (32 °F). Without these crystals water wouldsupercool instead offreezing. This method can produce snow when thewet-bulbtemperatureof the air is as high as -2 °C (28.4 °F). The lower the air temperatureis, the more and the better snow acannon can make. This is the main reason snow cannons are usuallyoperated in the night. The mix of all water and air streams andtheir relative pressures is crucial to the amount of snow made and itsquality.

If conditions are below the curve snow can be made.
Wet-bulb temperature is considerably lower thandry-bulb temperature when airrelative humidityis low. Wet-bulb temperature takes into account that the waterdroplets cool themselves by evaporation. Artificial snow can be madewhen the (dry-bulb) air temperature is as high as 4.5 °C (40°F).
Modern snow cannons are fully computerized and can operate autonomously or be remotely controlled from a central location.Operational parameters are: starting and stopping time, quality of snow, max. wet-bulb temperature in which to operate, max.windspeed, horizontal and vertical orientation, sweeping angle to cover a wider area, sweeping may follow wind direction.
The snow cannon was invented by Art Hunt, Dave Richey and Wayne Pierce in 1950[1][2], who went on to patent it.[3]
References
^Machines Let Resorts Please Skiers When Nature Won‘t.New York Times (2001-02-02).
^Making Snow. About.com. Retrieved on 2006-12-16.
^US (1950-12-14) W. M. Pierce, Jr. Method for Making and Distributing Snow
See Also
Artificial ski slopes
Snow grooming