ROANOKE, Va. – If you were in parts of Grayson or Carroll Counties Wednesday afternoon, you may have just settled down for a long winter's nap. Then BAM! Thunder and lightning, seemingly out of nowhere, woke you up. We also heard a report of thunder in Martinsville!
You weren't dreaming. That was real! While freezing rain was icing things over, a thunderstorm developed. We have the lightning data to confirm that in the picture above.
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How in the heck can a thunderstorm form, when it's 31 or 32° outside?
Here's how. Thunderstorms typically develop when there's cold air above warm air. That warm air has to be rising, though, in order for the storm cloud to form and for precipitation to develop.
While it was freezing here, the temperature at the 3,000 foot level was 51°F. When we took a 3-D scan of the radar, it showed that the storm was only 10,000 feet tall. (Most summer storms are around 30,000 or 40,000 tall.)
At the 10,000 foot level, the temperature were 12°F. So, you had that temperature differential.
The air was already being lifted.
The difference in electrical charges between the top and bottom of the cloud helped spark lightning.
Crazy that we saw that, in addition to all the wintry weather we've seen Wednesday as well.