The "Magic Line"

Since Cody didn't fill you all in on the "Magic Line" . . . I will :) When we are forecasting for snow, like we're seeing today, there's a line we look for, it's called the 540 line. The 540 corresponds to 5,400 geopotential meter thickness of the atmosphere between 1000 and 500 millibars. Basically warm air takes up more space in the atmosphere than cold air does, so when we've got warm air in place, our thicknesses have higher values. (think of how a balloon gets smaller when you take it from hot air to cold air) Check out this experiment below if you want to see it in action for yourself - fun thing to do with the kids.When cold air moves in, the thickness of the atmosphere decreases and the 540 line is somewhat a guide as to when the air is cold enough to produce snow showers instead of rain showers. If that doesn't make much sense and you'd like it to, check out Jeff Haby's site, he goes more in depth when it comes to thickness. But basically the more thickness decreases in the atmosphere, the better chances there is for snow. And the 540 line is the thickness that normally separates rain from snow showers to occur.

So when we're looking at the models to figure out the forecast we look for this magical line first to see if there's a possibility of snowshowers. If the thickness is less than 540, that's even colder air, so there's an even better chance for snow versus rain showers. With the thickness line at 526 around our area today... we're going to stick with mainly snow today that will exit by the evening hours, just in time for Thanksgiving!

Enjoy Thanksgiving Eve!

~KDLT Meteorologist Jesse Ritka