We have a complicated forecast shaping up for this weekend, so please understand that there is going to be a lot of uncertainty regarding this potential ice storm. I suppose I could have waited a little longer before I put out this forecast, but these kinds of potential winter storms are complicated to forecast even a day before they happen. I figured I might as well share my early thinking. In this article, my goal is to detail the projected overall setup this weekend into next week and explain why this COULD lead to a significant ice storm across parts of the Southeast. Notice that I used the word ‘could.’
A potentially record-breaking high pressure system is currently moving into the United States and will be responsible for the brutal cold that the majority of us will experience this week. Like I explained several days ago, these high pressure systems can bring really cold air with them by pulling the cold air down from Canada as they move into the U.S.
Once we move into this weekend, everything gets very interesting, and anytime I tell you that things are getting interesting, you know what that means. Another high pressure system is going to be moving south and east from Canada later this week and will be located near the East Coast by the end of this weekend. Because of the location of this high pressure system, the clockwise flow around this high is going to wrap around cold air from the north and cause it to dam up east of the Appalachian mountains. This is what is called ‘cold air damming’ in meteorology. The cold air can’t keep past those high mountains so it pools at the base of the mountains. In this type of scenario, you can actually have the mountain tops warmer than the valleys.
As you can imagine, if you get any kind of moisture to move over those areas at the same time, then you can have major icing issues. In many cases, the cold air is shallow, and the air above the surface is above freezing. Instead of the white, beautiful snow, you get a nasty ice storm instead.
After this high pressure system moves off the coast late this weekend, we have ANOTHER strong high pressure that will be moving across Canada and eventually over the Great Lakes and Northeast regions. This is going to set up a classic cold air damming situation east of the Appalachians, and if moisture is available, southeast regions of the U.S. will have another shot at an ice storm.
With all of that said, there could be two cold air damming scenarios setting up back to back.
What In The World Does All Of This Mean?
I’m going to tell you right out of the chute that forecast models handle these types of setups horribly. In the past, residents across the Southeast have gone to bed thinking they’re going to get a rainstorm and wake to a crippling ice storm or vice versa. Forecast models typically underestimate the amount of cold that will be in place with cold air damming scenarios, and in some cases, underestimate the amount of moisture over the region.
This weekend, moisture should begin to get pulled up from the Gulf of Mexico. Initially, places like eastern Texas, northern Louisiana, Arkansas, and eventually regions north and eastward could get freezing rain and sleet. As cold air starts to build east of the mountains later in the weekend, any moisture that moves over the region could be freezing rain and maybe some sleet. Regions that I am watching particularly close late this weekend are northern Georgia, Upstate South Carolina, central and eastern North Carolina, and southeastern Virginia. Please understand that areas just outside of those regions also need to keep a close watch on things.
Another ice storm treat could be possible early next week around Tuesday, and the regions that I am watching most closely are central and eastern Georgia, Upstate and central South Carolina, central and eastern North Carolina, and southeastern Virginia. Northern portions of Alabama may also need to be monitored.
It’s all going to come down to if a) adequate cold air is available and if b) the moisture doesn’t go south of the regions mentioned above. Again, I can’t stress enough how horribly forecast models handle these types of setups, so your mobile weather apps that give you a weekly forecast will pretty much be useless right now.
Don’t go buying up all of the bread and milk just yet. We have a couple days to really watch everything, and I will be coming out with another forecast as things get a little more concrete. Residents located in the possible impact areas need to keep watching everything very closely, and if you rely on my forecasts to make your plans, be sure to check back on this site multiple times a day. These high uncertainty forecasts are subject to change.
I may have an article coming out tomorrow, explaining how all of this ties into my original winter forecast. I would have included that in this article but didn’t want to make this post too long.