[Geezer (OP)]

It's a beautiful day today. There is not a cloud in the sky. So how come it's snowing???

I can see little snowflakes coming down all over the place. Is this the work of snow fairies or aliens?

[imatfaal]

It's your alien kin coming back to reclaim you.

[CliffordK]

How close is Chernobyl?

[Geezer (OP)]

Sheesh! I'm beginning to understand how Rodney Dangerfield felt.

[CliffordK]

How cold is it outside?  Below 10°F?  Relative Humidity?

I would think that an ice crystal could begin to grow right at the dew point, then start to descend without necessitating the formation of clouds, but perhaps only when it is really cold out.

[Geezer (OP)]

It was in the mid to upper twenties. No idea about the RH, but not very high I would guess. No wind though.

It did it most of the day. It could be a lake effect I suppose, but visibility was very good. It had to be crystallizing out of the atmosphere somehow. Maybe some sort of inversion effect?

[CliffordK]

There was a question earlier about what makes a cloud float.
http://www.thenakedscientists.com/forum/index.php?topic=36364.0

Obviously your clouds lost their buoyancy!!!

My conclusion was that it was likely a dynamic process.  While you may have updrafts and etc...  However, at some level, say 1000 feet, the air has a relative humidity, and temperature to support the creation of a cloud.  However, at 900 feet, it doesn't.  So, should a droplet fall from 1000 feet to 900 feet, it would tend to evaporate back into the vapor phase, at which point, due to the lightweight H₂O molecule, it would start to ascend again back up to 1000 feet where it could condense again.

However at colder temperatures, more uniform humidity, etc...  rather than evaporating, the droplet/snowflake may continue to fall, and for a time at least, continue to absorb moisture from the environment.

[Don_1]

What have you been drinking?

[Bill.D.Katt.]

This might be the phenomenon known as diamond dust. http://en.wikipedia.org/wiki/Diamond_dust

[yor_on]

"At very cold temperatures, 40 below zero (C or F) and colder, snow can actually fall out of the cleanest, clearest blue sky without intervening clouds. Temperatures need not be so cold if there is dust, or other minute particles, in the air on which the water vapour may deposit. When condensation nuclei are present, diamond dust may form at temperatures just below minus 20oC (0 oF). At such temperatures, the water vapour in the air spontaneously forms ice crystals which slowly settle earthward. When these falling crystals are caught in the light, they sparkle like gemstones, a weather condition known appropriately enough as diamond dust." And "ice crystals form as irregular hexagonal plates, or as unbranched ice needles or ice columns directly from water vapour in the air. The formation of hexagonal-plate crystals is favoured at air temperatures from minus 10oC to minus 20oC (14oF to minus 4oF). Ice plates resemble dinner plates with a hexagonal pattern in their long dimension and are thin relative to their width. Ice columns, on the other hand, look like minute stubby pencils. Columns typically form in temperatures below minus 25oC ( minus 13oF). "