The “Wedge”…what is it anyway?
In the Carolinas, we often get into a very cool, wet and breezy weather pattern that can last for days. This same set up, known to meteorologists as the "wedge" is also responsible for most winter weather we get in Eastern Carolina.The "wedge" is a clever name for when a shallow layer of cold air near the surface dams up against the Appalachian Mountains leaving us socked into cold and damp weather for days at a time. It usually occurs a couple of days after a cold front moves through the area leaving a cold area of high pressure in place across New England. Clockwise flow around that area of high pressure causes our winds to be from the northeast for typically 1-2 days. This happens any time a cold front moves through, but what makes the wedge possible is when the winds aloft shift to a warm and drier west or southwest flow. This causes a temperature inversion to form (when temperatures get warmer with height instead of cooler like normal). Underneath this inversion, we get a layer of very cold and often very damp air that "dams up" against the Appalachian Mountains to our west due to the fact the heavy cold air can't quite get over the top of the mountain peaks. The result: cloudy, breezy, cold and often drizzly day in Eastern Carolina, just like we have seen for the past 2 days.
As a matter of fact, most ice storms we get in Eastern Carolina are caused by the wedge. This is because disturbances in the upper level westerly flow can move over the thin subfreezing layer near the surface giving us freezing rain and sleet. Of course, in the spring and summer, it's much too warm for wintry weather, but every now and then, we can actually get a "cold day in July" so to speak where it's cloudy, wet and breezy with highs in the 50s and 60s.
So, next time we have a day like that this summer, watch me on News13 and see if there isn't a big blue "H" over New England! Come back later today and I'll have a sample surface map to show you what it looks like.
Posted by on 04/08 at 07:56 AM
Chris, During the spring semester of my freshman year at USC (2003), I remember a local meteorologists talking about a weather feature that was causing the wet conditions the city was experiencing at that time. I can’t recall the exact term he used but it had the word Omega in it. Then he showed a graphic on his weather map of some sort of stream going across the country in the shape of the greek letter Omega. Can you tell me what this is?
Jamie