I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

Charles wrote:
I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

With the Bartlett High (of the ancillary thread here) there is a
tendency toward foggy weather. If the snow was behaving the way vapour
behaves in a mist or cloud that would explain it.

We know that snow does accumulate in the tops of clouds and mists are
no more than clouds at very near ground level. So that just leaves the
behavior of vapour to be explained.

On 1 Jan 2007 15:06:09 -0800, "Weatherlawyer"
wrote:


Charles wrote:
I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

With the Bartlett High (of the ancillary thread here) there is a
tendency toward foggy weather. If the snow was behaving the way vapour
behaves in a mist or cloud that would explain it.

We know that snow does accumulate in the tops of clouds and mists are
no more than clouds at very near ground level. So that just leaves the
behavior of vapour to be explained.


This was clear, mostly sunny, suitable for driving about 70 MPH
(bigger number in KPH)

Charles wrote:
On 1 Jan:06:09 -0800, "Weatherlawyer"
wrote:


Charles wrote:
I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

With the Bartlett High (of the ancillary thread here) there is a
tendency toward foggy weather. If the snow was behaving the way vapour
behaves in a mist or cloud that would explain it.

We know that snow does accumulate in the tops of clouds and mists are
no more than clouds at very near ground level. So that just leaves the
behavior of vapour to be explained.


This was clear, mostly sunny, suitable for driving about 70 MPH
(bigger number in KPH)

An high is an anticyclone and just above the mist would be a clear
cloudless sky. The mist I alluded to might well have been of to the
side and the snow drifted out. or, more likely, the entire volume being
frozen, it would no longer absorb light as vapour does but reflect it
as snow does?

I'm only guessing. And the conditions in Britain where there are only
the very tops of a very few hills anywhere near high enough to get that
sort of thing, so it is very rare here.

And that's presuming I am right.

On 1 Jan 2007 16:20:11 -0800, "Weatherlawyer"
wrote:


Charles wrote:
On 1 Jan:06:09 -0800, "Weatherlawyer"
wrote:


Charles wrote:
I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

With the Bartlett High (of the ancillary thread here) there is a
tendency toward foggy weather. If the snow was behaving the way vapour
behaves in a mist or cloud that would explain it.

We know that snow does accumulate in the tops of clouds and mists are
no more than clouds at very near ground level. So that just leaves the
behavior of vapour to be explained.


This was clear, mostly sunny, suitable for driving about 70 MPH
(bigger number in KPH)

An high is an anticyclone and just above the mist would be a clear
cloudless sky. The mist I alluded to might well have been of to the
side and the snow drifted out. or, more likely, the entire volume being
frozen, it would no longer absorb light as vapour does but reflect it
as snow does?

I'm only guessing. And the conditions in Britain where there are only
the very tops of a very few hills anywhere near high enough to get that
sort of thing, so it is very rare here.

And that's presuming I am right.


I guess I didn't frame my question well enough.

Charles wrote:
On 1 Jan:20:11 -0800, "Weatherlawyer"
wrote:


Charles wrote:
On 1 Jan:06:09 -0800, "Weatherlawyer"
wrote:


Charles wrote:
I was driving on a freeway at about 4000 ft elevation, daytime, air
temp about 45 F, snow in the air but no accumulation on the ground.

It appeared that there was an area about 2 to 4 inches above the
ground where the snow was very much denser and I was able to watch the
air currents from cars and just the wind move the snow around. Snow
above this layer was quite thin, it wasn't snowing hard.

What was going on that would cause the snow to float just above the
ground like this? why doesn't it just fall all the way to the ground
and melt there?

With the Bartlett High (of the ancillary thread here) there is a
tendency toward foggy weather. If the snow was behaving the way vapour
behaves in a mist or cloud that would explain it.

We know that snow does accumulate in the tops of clouds and mists are
no more than clouds at very near ground level. So that just leaves the
behavior of vapour to be explained.


This was clear, mostly sunny, suitable for driving about 70 MPH
(bigger number in KPH)

An high is an anticyclone and just above the mist would be a clear
cloudless sky. The mist I alluded to might well have been of to the
side and the snow drifted out. or, more likely, the entire volume being
frozen, it would no longer absorb light as vapour does but reflect it
as snow does?

I'm only guessing. And the conditions in Britain where there are only
the very tops of a very few hills anywhere near high enough to get that
sort of thing, so it is very rare here.

And that's presuming I am right.


I guess I didn't frame my question well enough.

Take a look at the FAQs on Frosts at the uk.sci.weather site. There can
be substantial temperature differences in very thin layers just above
ground level. And of course a lot depends on adiabatics in the above OP.