2012 Will Begin With An Arctic Plunge

GFS model forecast for Monday morning

This time of year, we keep a sharp eye on the red line.

The “red” or pinkish looking line in the graphic above is called “the 540 line”.  Those of us in weather pay attention to this line because it’s a measurement of air thickness between 1000 and 500 millibars.  High thickness of combined temperature and moisture in this area would produce an atmosphere too warm for snow.  Low thickness (540mb or lower) means the air is “thin” enough for snow to reach the ground.

Many forecasters also refer to the 540 line as “the rain/snow line” but it also acts a good indicator of where very cold air may make its presence known.

As you can see from the map above, the 540 line drops well south into the Tennessee Valley on Monday as a deep low pressure system tightens and strengthens over southern Canada.  While we’re not concerned about rain vs. snow, we will be looking at a big surge of cold air beginning Monday and hanging around a day or two.

Longer range models show the Arctic plunge will be short-lived and does not look to produce any snow around Southern Kentucky.

So, we leave the old year warm…and ring in the new year freezing!