Autumn arrives ... at its worst

You know those beautiful crisp autumn days, when the color of the leaves contrasts against the clear blue sky?

Well, forget about it for a while.

We're facing two days of autumn at its worst, courtesy of a Carolinas specialty -- cold air damming.

And when that event ends, it'll be replaced by an invasion of the coldest air we've experienced since last spring.

After weeks in which it seemed as if daytime temperatures in the 70s and 80s would stay with us forever, some really chilly air is filtering into the Carolinas. Highs today will reach the 60s, thanks to sunshine.

But low pressure will form in the Gulf of Mexico later today and then move up the East Coast later Wednesday and Thursday. At the same time, high pressure over the Northeast will send a flow of chilly air into the Carolinas.

Cold air, being heavy, sinks. This cold air will pile up against the mountains, and clouds will form. High temperatures Wednesday and Thursday won't escape the 50s, and there'll be a chilly northeast breeze to make things worse. This situation is called cold air damming, because the cold air is dammed up against the mountains.

In such an event, sunshine and temperatures 10 to 15 degrees warmer often can be found on the western side of the mountains.

The low pressure system moving up the Carolinas coast won't be strong enough to produce much rain, and the Charlotte area won't get much more than 1/10 to 1/4 of an inch, mostly from noon Thursday to early Friday. But with the gloomy skies, it'll be rather ugly around here for a few days.

On Friday, a cold front will wash out the chilly, damp air. But it also will bring winter-like temperatures, with Saturday's highs only reaching the low to mid 50s. Morning lows Saturday probably will be around freezing, and that will put an end to the growing season for much of the area.