The pattern we've had last week is a clear La Nina signal with a negative PNA producing the trough in the west and pumping the ridge in the south and east. The negative PNA affected the outcome of the large scale cold I was forecasting for November. The cold certainly developed, but had a hard time coming south and east due to the orientation of the Greenland blocking and massive southwesterly flow regime aloft.
The pattern evolving for the first few weeks of December will probably be our BEST chance of any snow this winter if you live anywhere from the southern plains, southeast, Ohio valley, and eastern seaboard. We have a negative AO/NAO combination right now and with the MJO going near Octant three this supports a trough in the east. We also have stratospheric warming commencing despite a west based QBO and this will displace the cold over the pole farther south and east. With continued height rises and blocking expected to retrograde I am compelled to say that our most significant arctic intrusion yet is underway. With a trough developing over the east this puts most of the country in a northwest flow aloft. So instead of lake cutting systems(like the current one), systems are apt to go more east or southeast and this will put the aforementioned regions in a favorable pattern for wintry precipitation. What is interesting is the fact that the LRC theory is emerging. Remember the period of the omega blocking then amplified closed lows over the southwest translating east? This pattern could be redeveloping which will prove to be VERY interesting for many as this time there will be a lot more cold in the pattern.
After Christmas the AO is likely headed dominantly positive with a raging west based QBO. This translates to a classic La Nina signal on our pattern which develops the ridge over the southeast and trough northwest. The NAO is still somewhat of a wild card.