A quick question...

[wx247]

This afternoon our high reached 41 and during the mid-afternoon hours when it was hovering around 40 it began snowing down hard. This lasted for about 35 minutes and then it quit.

My question is this: is there any certain temperature that it has to be at the surface before it can't snow? I know that the 850 mb area has to be below 0, but what about surface temps?

Thanks!
Garrett

[Stormsfury]

Actually, there's no true limit that I can think up. Just as long as a snowflake doesn't melt by the time it hits the surface.
Obviously, as you stated, first the levels above must be capable/cold enough for snow growth. The highest temperature at the surface I've seen was 48 with snow and sleet (This happened in NC a couple of years ago). Very steep lapse rates due to an upper-level low. WBZ (Wet-Bulb Zero) temperatures determine p-type.

I've seen snow occur at 41. (Dewpoint was 27.) As soon as the snow started, the temperature fell 3 degrees rapidly. The profile of the atmosphere was of a convective nature. Large Cumulus clouds indicative of an unstable atmosphere. If I'm not mistaken, temperatures at the 950mb level were in the low 20's. when this happened.

[wx247]

Thanks! That makes a lot of sense. It was a convective snow, so you cleared a lot of info. up for me.

Garrett