
October wedge.
Last month we had a rather unique weather situation occur. We had a wedge of cool air over us while at the same time, a Cat 2 hurricane named Francine moved into Louisiana. Normally, a hurricane moving into that part of the country, would travel northeast and have a major impact in north Georgia with wind, rain, and tropical tornadoes. Not this time.
The wedge was so strong, it forced Francine to move due north into Arkansas, limiting the impacts to our area. All we saw was some patchy drizzle and a few light showers. The computer models really struggled with the rainfall amounts, most indicating 1-4 inches with isolated higher totals. I think most of us ended up with less than .20”, if that.
My first encounter with a high pressure wedge was in January of 1982. I began my meteorology career with NBC in West Palm Beach, Fla. in 1976. In 1978 the NBC station in Minneapolis hired me and also paid for my graduate school at the University of Minnesota. Needless to say I learned a lot about winter weather! In 1982, WSB in Atlanta called and invited me to work for them. When I got the call from the news director, the temperature outside was 35 below zero! Being from the south, it was a no-brainer.
Arriving in Atlanta with my family on January 13th, was a total shock. Cars all over the road, abandoned. No hotel rooms. Most everything was shut down because of what was now called “Snowjam ‘82.”
Everyone said it was a surprise ice and snowstorm. I just thought, how could a storm of this magnitude be a “surprise”? Turns out, it had to do with a “wedge.”
I thought now would be a good time to explain exactly what a wedge is, since fall and winter is prime time for these unique creatures of weather. See accompanying graphic showing a perfect example of a wedge. I know it may be difficult to see, but this is the actual weather map on January 14, 1982. This of course, was well before computers and we would get the maps every day via fax.

Temperature map during a weather wedge.
This was the set-up. We had a strong and very cold Canadian high pressure across New England. The lines around the high are called isobars, lines of equal barometric pressure. They define where the high pressure is. Notice the little “kink” in the isobars down through North Carolina. That shows me there is a wedge of cold air in place and heading for us. Winds flow clockwise around high pressure. Cold air is thick and dense and behaves like syrup. When the cold air gets pushed up against the side of the Appalachian Mountains, it gets funneled down the side of the mountain into north Georgia. Also shown is a temperature map showing what temperatures look like in a winter wedge.
At the same time this cold air is plunging southward, you will notice back on that 1982 map, low pressure riding northward, out of the Gulf of Mexico. It was spreading warm tropical air with a lot of rain north. Again, think of cold air like syrup and warm air like feathers. The warm air cannot push the cold air away so it goes up and over the top of the wedge. As the rain falls, it hits the subfreezing pavement and then we have our worst case scenario: an ice storm.
I promised when I began working at WSB there were not going to be any more “surprise” winter weather events. That promise has carried over to the new team.
As we enter “wedge” season, for now expect cool and drizzly conditions from this unique creature of weather in the South when they occasionally move in. Otherwise, enjoy the fall color and that beautiful October sky!
Graphic: courtesy NWS