This winter is about to get very active and cold, and it’s going to happen fast. I have been saying for several weeks now that the most memorable part of this winter could be the last week of January going into the first couple of weeks in February. Even beyond that, the weather could remain very cold and active, but I’ll begin discussing that timeframe when we get closer to it.
Some of you have pointed out to me that your weather apps and local meteorologists are predicting a moderation in temperatures, and for a few days, temperatures are going to be warmer for many. It’s important to point out that this January was not the blowtorch that many began to predict once the entire month of December ended up warm, and this coming warmup is only going to be moderate. Despite the absence of upper-level blocking over Greenland and the Arctic in January, it has remained very cold. That’s very important to take note of, and I’ll explain why later in the article.
I mentioned several times that it seems to me that what kept us warm in December and forced the unfavorable upper-level pattern setup in January was an abnormally strong Pacific jet stream that was pushing all of that warm, Pacific air in a west-to-east motion. There were other factors at play also, but I believe that they were being weighed too heavily in the meteorological community. What’s ironic about this is that January HAS been very cold for most of the United States with the exception of the West Coast and parts of Florida. Let’s not forget that we live at the surface and not in the upper-levels of the atmosphere. Again, that has strong implications and further confirms with me what has been the main driver of this winter.
What Is The EPO, and Why Is It So Important?
EPO stands for Eastern Pacific Oscillation, and once again, I believe that it is in the driver’s seat this winter and has been. The EPO is an index that measures the amount of blocking, or lack thereof, over portions of the West Coast and Alaska. During a negative EPO, temperatures tend to be warmer over Alaska and over the western United States and colder in the central and eastern United States. This was a HUGE driver that brought the bitter cold that we experienced last winter, which is why I explained why we didn’t need a huge amount of blocking over Greenland to get cold into the United States. We saw how last winter turned out, and as you know, it wasn’t on the warm side of things.
As expected, we are about to experience a brief warmup, and it just so happens that the EPO is now in its positive phase. That will only be brief, and model guidance brings the EPO back into it’s strongly negative phase, just as model guidance is projecting a potentially significant Arctic blast during the last week of January and likely extending well into February.
The main culprit behind the EPO being so negative over the last two winters has been the warm pool located in the northeast Pacific. It was there last winter, and it is still there today. As the Pacific jet stream (the band of really strong winds in the upper-levels) begins to relax somewhat, the negative EPO should become an even stronger player.
Why I Believe The Last Week Of January Into The First Couple Weeks Of February Will Be The Most Memorable Part Of This Winter?
As I mentioned above, I believe that I have correctly identified what delayed the cold in the second half of December, and the index that kept us cold in January, despite the lack of ridging over Greenland and the Arctic. Those cold Arctic high pressure systems kept the cold air funneling south into the United States earlier this month, but for the snow lovers along the East Coast and the South, the snowfall totals have not been that great thus far. It’s not unusual for the Southeast not to see snow or ice until later in January or February, but it has been unusually snowless in the Mid-Atlantic and Northeast. That could change in a hurry.
The upper-level pattern could begin to shift from a non-favorable pattern for East Coast winter storms to a much more favorable pattern for bigger storms riding up the coast. It’s important to point out that regions all along the South will continue to be under the gun regardless of what happens due to a very active sub-tropical jet stream. If any amount of cold air is in the right place at the right time with adequate moisture, parts of the southern U.S. could get snowy/icy conditions later this month into February. The big question right now is whether or not these storms will strengthen and pull up the East Coast.
I know that I explained that a strongly negative EPO alone can bring colder conditions to the central and eastern United States, but the latest model guidance continues to strongly hint at blocking setting up over the Arctic and Greenland. That would further reinforce the brutal cold over the central and eastern United States and greatly increase the chance of big winter storms moving across the South and up the East Coast.
I also recently discussed that the recent warming of the stratosphere could weaken and even potentially split the polar vortex. Warming over the North Pole like that typically has effects a few weeks down the road, and if the pattern is right over a particular region, brutal cold across the mid-latiudes can be the result.
The regions that will be impacted by the brutal cold will be the Great Plains, the Upper Midwest, the Ohio River Valley, the Tennessee Valley, the Northeast and Mid-Atlantic, and the Southeast. So basically, that covers about everyone east of the Rockies. While the focus of the cold air so far as been over the Great Plains (further west), the core of the cold could shift slightly to the east. That will be interesting to see how that evolves. Again, the period that I am watching most closely is the last week of January into the first couple weeks of February. After that, the pattern could continue to remain active and cold.
Major Winter Storm Potential In About 8 to 10 Days:
Before I end this article, I want to discuss the potential for a major winter storm around this timeframe. I am more confident than usual that there will be a pretty sizable winter storm during this period. What is currently happening around the globe supports this event occurring, and recent model guidance has continued to support this potential. It’s important to note that model guidance will likely be all over the place this far out, but again, the other factors that I look at to make my long-range forecasts strongly support this.
Given that guidance has continued to show blocking setting up over Greenland and the Arctic, I am leaning more towards this system moving across the southern United States and eventually up the East Coast. That could change given that this storm could occur just as we are transitioning into a much colder pattern. Like I mentioned above, the EPO will continue to be a big driver this winter, so even a neutral or slightly negative NAO/AO would probably do the trick. Still, the more negative those teleconnections are, the better!
At this point, I can’t tell you if you’re going to get snow or ice in YOUR backyard. What I can tell you is that a storm will likely develop, and wintry weather chances will be on the increase. There could even be another storm several days later, but let’s not get ahead of ourselves just yet.
Given the changing pattern, wintry weather chances will likely increase for the Southern Plains, the Upper Midwest, the Ohio River Valley, the Southeast, the Mid-Atlantic, and the Northeast. I may have left out some locations, but I’m just trying to give you a general idea at this point.
The pattern could shift very cold for the central and eastern United States towards the last week of January. If this does occur, temperatures, as a whole for this month, could be just as cold or colder than last January. Records could be challenged or broken in certain regions.
A big winter storm could take place in about 8 to 10 days. Details are still uncertain, but I am more confident that a larger winter storm will develop.
The pattern will remain active, and several Arctic blasts are possible between the last week of January going into February. Several winter storms are possible.
Winter isn’t over like so many seem to believe. What is currently occurring compares quite well with winters that are similar to this one. There are some differences, but there are definitely some major similarities.
Matthew Holliday (Curriculum Vitae - Resume) is a graduate of the University of Oklahoma, where he completed a B.S. in Meteorology and a B.S. in Geographic Information Science. He completed his master's degree in meteorology and climatology at Mississippi State University and is currently pursing a Ph.D. in Earth and Atmospheric Sciences.