BLOG: What is the highest temperature snow will fall? - | WBTV Charlotte

BLOG: What is the highest temperature snow will fall?


Before we completely forget about winter, I thought I'd address this question we get from time to time.  Charlotte almost always seems to be on the bleeding edge of winter storms and inevitably we forecasters are trying to pinpoint which areas will receive rain, snow, sleet or freezing rain. But beyond that, often times it seems like the weather is backwards on the edge of these storms.  It may be snowing when we're above freezing, or it might be raining when we're below freezing.  What gives?  

Well make sure you take a look at the diagram I attached.  The atmosphere often times looks like a layer cake, with different layers at significantly different temperatures.  And that gives rise to the different types of winter precipitation we encounter.  Of course the old adage is, once you melt a snowflake, you can never get it back.  Oh it can refreeze again, but it will turn into an ice pellet, or more commonly known as sleet.  If it didn't have time to refreeze while falling, it can still refreeze after landing, and of course we call that freezing rain.  

In almost all cases, that plain ol' rain you see starts off as snow high up in the atmosphere, even during the stifling heat of the summer in a July thunderstorm.   And on the other side of things, if the air is above freezing on the ground, but very cold just above, snow can reach the ground before melting.  The warmest I've ever seen snow falling is 40°, but I've seen sleet reach the ground with surface temperatures as high as 50°.  That's because sleet falls faster and has less time to melt, and it also has less surface area than a snow flake which insulates it some from the warmer surrounding air.  

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