Is 'warm snow' possible? (snowfall, temperature, city, freezing)

[Glacierx]

Here is proof that it can snow above 40 F (note July 16th)... Daily Data

[Crunch41]

^Wow, snow in July at at 51N? Impressive.


Chris Burt from Weather Underground mentioned two freak summer snowfalls in the Great Lakes region: 8" in the middle of a hailstorm in July in Indiana, and a slushy 5" on August 8, 1882 accumulating on a boat in Lake Michigan.

Quote from the Indiana one:
page 3 of this pdf journals.iupui.edu/index.php/ias/article/download/5268/5199‎

Rarely the hail is so small as to closely resemble snow. A remarkable
summer snow storm in Indiana is worthy of mention here.
"The most remarkable warm season snowfall in Indiana occurred
on July 2, 1924, in Wabash county. There, with the temperature at the
nearest Weather Bureau Station nearly 70 degrees, during a hail storm,
snow fell to a depth of eight inches on a small area."
An account of this remarkable fall was published in the Bulletin
of the American Meteorological Society for August, 1924, and the
report was investigated by J. H. Armington, state director of the
United States Weather Bureau, Indianapolis, who was convinced of the
correctness of the report. This remarkable snowfall was associated
with a violent hailstorm which had a distinct tornado-like funnel. Hail
covered the ground for some distance around the patch of snow.

For the Lake Michigan one, it's page 100 here

[Ethereal]

Originally Posted by AdriannaSmiling

In reality, no, I don't think it can fall above 40 F but in my fake climate, it snows in the tropics. I made the fake climate before I learned to alter the wikipedia climate boxes but if anyone requests, I can create a wiki box for this climate; http://www.city-data.com/forum/weath...mperature.html

Please do. I would like to see table and especially the Celsius conversion (yes, I'm lazy at Googling the converts).

[Patricius Maximus]

At one point earlier this year I saw a huge batch of snowflakes fall when it was 42F; that was according to my car thermometer, a portable thermometer, and was confirmed by the official stations. The relative humidity was 30% at the time and obviously the cloudtops were much colder than the ground; partly due to evaporative cooling the temperature wetbulbed to around freezing within a few minutes and it accumulated half an inch much later. Still, the warmest I ever saw more than a couple of slushy flakes was 38F, and I thought significant snow above 40F was nigh-impossible prior to that incident, since the relative humidity would be low enough to preclude clouds and precipitation, but apparently a surface humidity of 30% is more than enough.

It is a fact that snow can fall at very mild temperatures if the conditions are just right. This nifty calculator calculates the temperature at which falling snow will melt under different humidities, and under the conditions I witnessed (42F/30%) snowflakes will certainly make it to the ground if the temperature is 42F or lower. I can't imagine clouds and precip forming with relative humidites much under 20% or so, which would raise the melting temperature to 46F at most. Under perfect conditions, there would be a slim chance for snow to make it at 49F. Beyond that there's no hope at all. 49F would certainly qualify as "warm snows".

Now, you can get small hail as high as around 80F or so, but I don't count hail as snow.

[MeteoMan]

It snowed at 7°C in May 2010. Surface temperatures aren't that important compared with what's going on upstairs.

[Weidehond]

No

[Adi from the Brunswicks]

Yes for those living in Minnesota and North Dakota .

For them, anything above 35 F is bikini & trunks weather, and it has flurried here at those temperatures.

We are done with regards to snow this year, forecast predicts just cold rain from now on. UK climate has taken over .

[P London]

For snow there's needs to be colder air aloft so theoretically it can be 8c with very heavy snow if the upper atmospheric temperatures are low.

That's all I know.

[EduardoFinatto]

It "snowed" with around 4/5ºC (39/41ºF) here in 2006, of course there wasn't any accumulation. We only saw the little snowflakes in the air and they melted before falling to the ground.

[jehane]

A hailstone is a block of ice. A snowflake is a thin layer of ice. If the snowflake falls through a layer of warm air it will melt. If a hailstone falls through a layer of warm air the outside will melt. If the hailstone is large enough, there will still be some ice by the time it reaches the ground. Much less likely for the snowflake.