Cold Air Damming…in August?! Yeap.

It’s the meteorological phenomenon that can destroy or verify a meteorologist’s forecast. However, we usually look for it in the “winter” months.

Cold Air Damming.

High pressure builds in from the north and gets “dammed” or “wedged” against the Appalachian Mountains (Seen on a surface map by “kinking” in the isobars). Colder air is locked in at the surface with warmer air aloft. In the winter months, how thick that cold air layer determines who gets rain and who gets snow or something in between.

If you live in the Midlands of South Carolina, it’s the reason why sometimes Newberry, Fairfield, and Kershaw Counties get snow and Columbia gets rain. A few miles can and do make a difference.

It appears Mother Nature will give us a chance to dust off the Cold Air Damming thinking caps and put them to work in August.

So let’s get to it.

TuesNightThe GFS computer model shows a frontal boundary and associated upper-level trough finally making it into the Carolinas on Tuesday. That will give us increased chances for rain. However, this front will linger around for a few days. Thus, more chances for rain through mid-week.

That frontal boundary will slowly sag to the south of the Midlands Wed/Thurs. The rain chances don’t stop there.

Thurs18z 500mb anomaly

Another upper level trough moves in after that and continues our rain chances through the weekend.

Now while all of this is going on…winds will start to shift at the surface out of the north or northeast on Wednesday as high pressure ridges down the spine of the Appalachians. This is the beginning of the Cold Air Damming event.

Wed_night_HighThis means cloudy, rainy, and cooler conditions. How cool?

Temp Anomaly

Well, by Thursday afternoon, the GFS model is saying quite a bit below normal for parts of the Carolinas. Some spots in the upstate of South Carolina could be 20-25 degrees below normal. For the Midlands it looks like 10-15 degrees below normal. However, Newberry and Fairfield Counties could be cooler (going back to the original a few miles makes a difference comment).

The interesting thing about this Cold Air Damming event…it appears to get stronger.

Friday_18zSo the cloudy, rainy, and cooler conditions could drag on through the weekend. Notice the sharp contrast in temperatures over a short distance below. Could see a few thunderstorms as well, especially along the coast.


The Weather Prediction Center says this is the rainfall potential through Sunday. #Wet


Here’s what the forecast models are thinking with our temperatures at Columbia Metro Airport…this far out. Please note that our average daytime high is 91 degrees for this time of year.


So needless to say…it will be the talk of the town. Perhaps we need to rethink “Famously Hot?” At least for this year. 🙂

I vote yes for this weather in August…how about you?


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