Icing conditions: Moist in the air thats colder than zero degree celcius. Clouds, fog or mist can give icing. Depends from time 2 time how much water its contains. Mist usually dont give noticeble icing if the visibility is more then 1km. Freezing rain gives a lot of icing of course.

Ice pellets or snow grain is freezing rain that already has frozen, and is a evidence of icing conditions higher up...usually seen when U have a occluded front above you. Ice pellets/snow grain dont give you ice but it tells you that icing conditions is above you and that it is not unlikely to find freezing rain in any direction, it´ll depend on the occluded front and the temperature variation the front(´s) produces.

Snow: when it snows the snow effectively takes away moist. If you have 1000ft cloudbase and it starts to snow heavily, the cloud dissolves cause the falling snow 'eats' all the small water drops. Heavvy snow takes the clud base away and give you vertical visability instead...in most cases lot higher VV than the cloud base was.

I fly military helis 'on the artic cirlce', never seen the ice warning system even move the needle in snow.

Heavy (wet) snow in about zero degree celcius or above can, as many said before, can form lumps that comes loose and into a engine and make a flame out. This would be tha main reason for restrictions to fly in heavy snow.

*) All above would be the normal. Off course there´s allways exceptions. Being too sure that the normal only occurs probably makes you die when you find out that there is 'exceptions that cornfirmes the rules' :bored:

That is the Bergeron-Findeisen process working -the Saturation Vapour Pressure is different over ice and water at the same temperature so the water droplet evaporates and sublimes onto the ice crystal. So therefore the SCDs and the snowflakes must exist at the same time ne c'est pas?

If I may be so bold, both crab and ramen are correct, it just depends where you are flying.

If you are VFR a couple hundred feet AGL, in falling snow, clear of cloud, you will not get icing. It's just snow in clear air.

If you are IFR in cloud that is in the process of making snow, then I agree with Crab, you may get icing.

I would also like to make a distinction in the SCD size. It is microscopic when FORMING snow (attaching to nuclei)

The SCD size that is the worry in aviation can be almost as big as a raindrop.

Both SCD, with great differences in affect.