northgawx

The weather in North Georgia is about to get a little crazy, as it is across most of the eastern United States. Seen below is the official forecast from the Climate Prediction Center for temperatures from days 6-10 (this weekend into next week). That’s a 70% chance of below normal temps, folks, and not just a little below average, either, but we’ll get to that shortly.

First off let me say that this forecast is quite low confidence, due mostly to the extremely dynamic/anomalous nature of the upcoming pattern. This is a pattern unlike anything we have seen since the winter of 2010/2011, which I’m sure a few of you remember well.

There are quite a few potential scenarios with what will play out over the next week and a half, so lets get started.

***The GFS***

The GFS has been very consistent, along with the rest of the modeling world, with developing a ridiculously strong high pressure system over Greenland, as seen below on the 0z GFS from last night.

This ridiculously strong high pressure corresponds to a huge drop in the NAO as we head into this weekend, and helps to dislodge all the cold air currently over Canada and push it way south into the SE United States. The 12z GFS wasn’t quite as strong with the cold air over the SE, however it still shows significantly below normal temperatures across the entire region all the way down into most of Florida. Below is the forecast NAO from the 12z GFS. The drop is fairly obvious to even the casual observer.

These are levels of the NAO we haven’t seen in a while, so IF this blocking comes to pass, it will be very cold across the area. As far as actual snow/storms, the GFS continues to be likely a bit to progressive with the pattern and doesn’t get much of any storm going, but at this juncture that is by far the least of my worries, since the GFS’s track record with storms outside of about 1-3 days hasn’t been very good lately.

The GFS also shows western ridging during this time frame although it is not nearly as strong with the ridging as our next topic: the Euro.

***The Euro***

And next up, the good ole European. The image below is from the 12z Euro Ensemble, and as you can see it agrees with the GFS on a very strong -NAO (high pressure) system over northern Canada and Greenland. Where it diverges, however, is over the Pacific. ***IF*** the Western United States ridge being advertised by the Euro/Euro Ensembles/Euro control come to pass, I will be extraordinarily surprised if we make it the next week and a half without someone in MS/AL/GA/SC/NC/TN getting a good thumping of snow.

 

Ultimately what the Euro is showing is something we haven’t seen since 2010/2011, and that is dual blocking. A gorgeous western ridge/-NAO couplet. It is also showing some retrograding flow which the models handle notoriously badly.

What is retrograding flow? Well it isn’t the way your teachers graded papers back in the 50’s. It is basically when a weather anomaly moves opposite the regular flow. In this case, the high pressure system starts out over Europe and works its way east to west to wind up over Greenland, instead of moving the regular west to east.The models are notoriously horrible at predicting what happens during retrograding flow, though they sometimes do pick up on the big storms. Toss in the potential dual block and you have a very effective dart board for the models to play with.

The Euro is currently the snow weenie model of choice because for the past several runs it has been hinting at a snowstorm, *possibly big*, as we head into the weekend and into the first of next week. I tend to agree with the timing because until that point the flow will likely remain too suppressed to see anything (storms get shoved too far south to bring us precip). However, once the pattern begins to relax a little I see AMPLE opportunity for a snowstorm, and probably the best setup in, quite literally, at least a couple of years. All this said, the Euro is pretty much alone in the strength of the western ridge, and its ensembles are much more like our next subject: the GGEM.

***The GGEM***

The GGEM (the Canadian model) is very similar to the Euro with the retrograding flow look as well as shows dual blocking, though it is much more GFS-like in the strength of the west coast ridge (being less than the Euro). It doesn’t show any sort of storm however at this juncture in time, as I said with the GFS, that doesn’t particularly bother me.

***The UKMET***

The UKMET (British Model that only goes out through 120hrs) is remarkably similar to the GGEM/Euro as well, and agrees with the GFS out to its 120hrs.

So, what does all this mean? You have pretty much one camp including all models that show the block (high pressure) currently over northern Europe retrograding into an impressive block over Greenland, and in the same camp a set of models that show some sort of western ridging. The Euro is strongest with the western ridging, though it is consistent, with the rest of the models being of varying strengths less than that of the Euro. At this point in time, I have to side with the less strong western ridging given even the Euro’s ensembles fall more in line with the GGEM/GFS, but the Euro is a pretty hard to beat model in the long range so it may be onto something, we will just have to wait and see. Ultimately with either ridging, we are looking at a pretty good set-up for something to occur late this week and through the first of next week, and it could be very big. Anomalous patterns of this type have a history of producing cut-off lows, which help to bring snow to our area, sometimes in very big fashion. As I said before, do not be discouraged if the models aren’t showing anything right at the current time, because the pattern looks great.

I will continue to remain cautiously optimistic regarding this time period, and, just so folks don’t infer incorrectly, right now I am NOT FORECASTING A SNOWSTORM, but one thing is for sure: cold is coming and we have an awesome look for a potential big system coming up.

~TW