GREENSBORO, NC -- You've probably heard it before or even said it, "If it thunders during winter, snow is on the way within the next 10 days." It's an old forecasting rule used for generations in North Carolina. But does it really work?
We want to know what you think. Have you heard this before? Do you believe it? There is some logic behind this old rule. Here's the science behind it.
It all starts with the jet stream, which separates warmer air and cooler air across the United States at any given time. During the winter, the location of the jet stream really determines whether or not our weather will be warm or cold. If the jet stream is flat, the cold stays to the north, and the warmth stays to the south. But, if it's kinked up and down, the cold air dives into the U.S. on one side, with big warmth on the other side.
When the jet stream is far to our north, we can get unseasonably warm. If you have enough moisture in this type of weather, with a strong enough weather system, you can get thunderstorms to happen here in North Carolina during the winter. It's fairly rare, but for it to happen, you need this type of jet stream position.
The thing is, is that once the jet stream is this amplified, in a few days it will shift enough to provide yet another dramatic temperature shift. In this case, if you have thunderstorms, the jet stream shifting over the next 10 days can lead to some very cold air. As you know, just getting cold doesn't mean it's going to snow, but, if you have moisture and a weather system to come in at the same time, you can get snow to fall.
That's the scientific reasoning behind this rule working some of the time. But does it work every time? Just some of the time? Or hardly at all?
It's certainly an issue that creates a lot of weather buzz every time it thunders this time of year!
The WFMY Storm Team dug into the data and looked back over the last 5 years to determine how many times it actually did snow within 10 days after it thundered. Between December and March from 2012 through January 2017 there were 18 days with thunder at the Piedmont Triad International Airport. Of those 18 instances it only snowed six times within 10 days of the thunder. This results in a 33% success rate. In the end this doesn't completely disprove the folklore, but it probably shouldn't be counted on as a guarantee for snow.
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