Coming off an incredible week of record highs including setting a new all-time record high at 80 degrees, today (Dec. 15th) as been nothing short of amazing with the difference in weather as we have 'wedged' in. You'll often hear meteorologists talk about a wedge, cool to cold damp air trapped against the eastern slopes of the big North Carolina mountains in a sharp v-shaped wedge appearance. Here's an example, this picture shows the wedge shape and notice the coldest temperatures or shades of light blue to blue hug the eastern sides of the mountains in the foothills to western piedmont. This is the heart of any wedge or cold air damming event.
You'll notice in the map, we're definitely chilly to cold on this Saturday. Colors in the yellow or orange range are 60s and even 70s. This map shows most of our region in a temperature range of 34 - 47. These are the weather scenarios that can raise eyebrows for a forecaster as a cold wedge about 8 to 12 degrees colder can bring wicked ice or sleet storms. Boy, how we just love those!! 
Note the letter 'H' over New York with a pressure of 1037mb. That's a strong area of high pressure with a good supply of cold air over eastern Canada to tap into and drain it down the eastern side of the Appalachian mountains. You can get a sense of this happening by looking at the u-shape nature of the lines across the Carolinas (isobars). While this is happening, a large winter storm is moving up the Mississippi River Valley dragging good moisture into our area and yes, a potential soaking rain - hoooray! Rain into a cold wedge of air acts to cool the temperatures even more. This becomes an issue when the dew point temperature (how moist or dry the air is) is down into the 20s. We're very fortunate though to escape any risk of significant ice as the high over northern New England is not sliding over New York to New Jersey and anchoring in. It's moving steadily east. Because of this, we'll avoid a continuously strengthening high pressure bringing colder and colder temperatures into our area. Sort of a, brief shot of chilly air then gone. This was a close one for our area as the ingedients almost came together for a stronger wedge and possible bout of winter weather.
Incidentally, in this example chart, the pink shaded areas with blue, green... that's computer estimation of liquid in a rain guage over a 6 hour period. That light pink over us indicates really light rain or drizzle through 1pm Saturday. Brighter pinks and blues come in late in the day, or, soaking rain for us:)
