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I was looking for rare snow events on southern USA and I found this footage from local news in Louisiana, reporting a snowfall in New Orleans at December 11th 2008.
I know it had already snow before in NO but, then I looked into this england website: weatheronline-Louisiana in order to find temps. back at that day and it showed a high of 42F and a low of 37F.
Question is? Is it possible to snow in a day with that temps? Or are they wrong?
I have learned from elementary school that snow/sleet conditions are possible only when it's under 0 celsius or 32 fahreinheit.
I think under certain conditions it's possible to have snowfall in temperatures above freezing... I think I read somewhere that the warmest it has ever been in a snowfall was something like 8C/45F.
It can if the dew point is at or below 0°C / 32°F.
Snow at 8°C sound dubious but if there are very very steep low level lapse rates and deep convection in the area such as thundersnow then snow could still make it to the ground level in a strong cold downdraft before melting (but melt rapidly on contact) from a cumulonimbus cloud.
I remeber when it started "thundersnowing" once here in England a few years ago when the temperature was about 6-7°C (43-45°F).
Snowfall in temperatures above freezing is very common ... in fact, our highest moisture content snowfall and most abundant snowfall in the Rocky Mountain region is during the spring warmer months rather than the colder winter months.
Inland California mountain ranges get tons of snowfall at much higher than freezing temps, too, with a very high moisture content ... known as "sierra cement" to skiers. These ranges are at much lower altitudes than the continental divide ranges in the rocky mountains.
The determining factor is the relative humidity of the air at or near ground level, and the air temps that the formed snowflake descends through to reach the ground. With prevailing RH's below 20% for much of the rocky mountain region, it's possible ... and I've seen it many times at ski area bases at 8,500' ... for snowfall to reach the ground in low 40F temps (6C).
Here at my ranch at just under 6,00' elevation, we had an inch of snowfall accumulate one night this week and the air temp didn't get below 35F. Of course, with the recent spring weather patterns and sunshine, the snow melted within a few hours after daybreak.
Yep, a lot of the snow we get in this country is very close to freezing, often a degree or two above. In February/March 2005 we had 16 straight days of snow falling (probably a record, I don't know), but it only stuck to the ground when the dewpoint was at or below freezing, and generally melted quite fast. In spring showers I've seen snow fall at 5 or 6C, but it doesn't stick.
Yes, ricardo. In fact, when it started to snow in Buenos Aires on July 7, 2007, the temperature was between 3 and 4 C (37 - 39 F) and indeed the temp never went below freezing during the 8 hours or so that the snowfall lasted. It stuck only in parks and green areas, but not on the streets. (It did stick in the suburbs). The low for that day I think it was 0.8 C in the city proper.
If the air is dry the snowflakes will continue to be chilled from evaporation.
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