Over the last week we have seen weather models all over the place in the long range. The important thing to focus on is that the atmosphere is stretched to extremes at the moment and this is going to mean more volatility in the day ahead. The best way to look at this is to view the upper air and the things that will be driving models to change further going forward. The way I see it is that the overall pattern will remain active. Even though we will moderate for a few days next week, Canadian cold air will be a player in some fashion. The questions are when where and how.
Looking at the teleconnection indices they are not only in extreme positions over the next week but they are also changing rapidly. The least important right now is the NAO which is positive right through Christmas but we have stated many times that of the 3 we look at the most this is the least important at the moment.
The two important ones are the Pacific North America index and the Eastern Pacific Oscillation. These indices basically describe the changes in pressure across their areas. The PNA goes strongly negative next week for a few days and then rises rapidly to neutral and then goes positive around Christmas. The Eastern Pacific Oscillation goes strongly negative toward Christmas and beyond. A negative EPO usually means cold for the East. The PNA going positive is a strong storm indicator for the east because it means there is a ridge in the west. The period where it crosses the neutral zone could be a good place for some sort of storm signal which would mean sometime around December 24-26...READ MORE AT http://www.meteorologistjoecioffi.com/index.php/2017/12/14/weather-models-remain-volatile-active-colder-long-range/