TheProfessor wrote:The GFS might be an extreme, but there are definitely hints of some colder air diving south in around the 12th or so. Ensemble members are great tools, but they shouldn't be taken verbatim(plus has the GEFS officially moved to the new version?) Anyways both the GEFS and EPS have troughs over the eastern U.S so there are signs for a cool down. The set up really is pretty interesting though, when you look at the teleconnections you have a positive NAO, which usually means the east coast is going to be on the warm side. However, the NAO has some things working against it. Right now the forecast is for the EPO to stay negative, the PNA to go very positive, and the AO to go negative, all those teleconnections favor cold filtering into the U.S. The positive PNA typically favors cold spilling eastward, but I do wonder if the positive NAO will help prevent that. I'm wondering if we could actually get a super interesting setup and end up with possibly a big East Coast or Midwest winter storm. The GFS does develop a subtropical ridge this up coming week, but quickly weakens it. If the GFS is weakening that ridge too quickly and you get a deep trough to dig in response to ridging in Canada and Alaska(due to the +PNA and -EPO) and you now have a boundary for a storm to form on. There are definitely some interesting factors at play here and any change to them could have drastic changes to the weather that the U.S sees.
Excellent post and observations. I wanted to follow up with what you were mentioning regarding the forecast of +PNA -EPO and +NAO by the middle of this month.
We had a situation.in.late December 2017.going into the first week of January 2018 in which we had the similar teleconnections set up which bought very cold temps and freezes to North Florida. Interesting thing to note was that the GFS, at that time , was very adament.on bringing that cold arctic air mass into the Deep South, similar to what today's GFS runs are showing to happen by mid month.
The GFS happened to be correct in not only with the arctic air coming south, but it also was correct.in forecasting a winter storm which occured across Southeast Georgia and into South Carolina in Jan 3-4 2018. The EURO initially missed the magnitude of the cold outbreak in the long range forecast (at least 10 days out) at that time.
So, a couple of things to point out here. The GFS indeed could be on to something here and it gave proof that a -EPO and + PNA can deliver cold arctic air into the Deep South despite a +NAO. It is something to really closely watch in the next few days. The situation that occured in the Deep South back in early January 2018 was handled very well by the GFS and I trusted the GFS that it was right back then with my forecasts, compared to the EURO and the GFS nailed it. So, the GFS has great merit with this situation and I am not saying it will happen exactly like this in 0a couple of weeks. However, all I am stating here is for folks in general to not scoff at what today"s Operational GFS is potentially indicating down the road.
next Sunday is near 70 Monday is in the 30s and falling 
