I am going to start off with something from my last blog that I think is important and will help determine which way we see the models go from here on out.  

Why the amplified solution?

The reason I am not liking a lot of these runs is the lack of ridging out west.  My reasoning can be seen on current IR imagery and the signs of a MJO phase 1.

Phase 1 MJO is highlighted in certain areas of enhanced convection.  The bonus part here which is kinda inhibiting a stronger signal (besides convection south of Sri Lanka) is the convection SW of HI which extends to the favorable phase 1 Mexico.  The convection near the dateline here is going to pump up the heights along the western US.  This would favor a setup closer to the GFS which could make things interesting if the model places the sfc features correctly.  

Phase 1 MJO composite:

Notice the higher height anomalies over the Western US.  This fits the overall tropical forcing perfectly.  

MODELS

GFS

After describing the upper level pattern above on the observations the GFS comes in with another completely different solution from 00z.  It flattens the ridge in response to the active Pacific which shifts everything.  The 50/50 low is weaker and more displaced and the system comes in at a higher latitude resulting in a warm inland system.  

Could this be the models resisting the change in the pattern? Yeah it might be as they don't want to build a ridge on the West coast, but I think we will continue to see this model flip flop.

The older GFS from 00z:

RPM

The RPM goes out to 72hrs and is a very good short range model.  It could have some big changes in this range but the overall upper level pattern is one that favors closer to my thinking than the GFS and CMC.  The trough is still digging in the Plains with heights much lower along the Eastern US.  This could be a sign of the models under developing the first system on the 17th.  The RPM is the most aggressive but not by too much  and as a result we see the changes!

CMC

Similar to the GFS aloft but develops a secondary a little too late for areas south of Southern New England.  Last run it did show accumulating snow possible all the way down to PHL on the back end.  Now it shifted north with that potential.  This model has also been flip flopping with every run.

EURO

Similar to the CMC with late secondary development and some backend snow for New England.  This model continues to flip flop also so now we are starting to see agreement on the inland solution with secondary transfer but there is still one problem.  I will address it in the "conclusion"

GFS ENSEMBLES ARE ALL OVER THE PLACE!

CONCLUSION

- Models have shifted from inland to coastal to out to sea to back inland all in the last few days.  This chaos will not stop because of all the systems in the Pacific and the one we are expecting this Sunday!

- This Sundays system will be the biggest player of the event.  The stronger this low can get the greater our chance for wintry precipitation in the Middle Atlantic and Northeast.  Models are not impressed but a few ensembles are and the RPM is leaning towards the more impressive side.   The ensemble member with the black dot is strong with the Sunday system and look how it impacts the forecast! That is a big time snow storm for portions of the Middle Atlantic and Northeast.  Others are strong and show a miss or earlier secondary development for a rain to snow situation.

- Whether rain or snow this system sets us up for a chance at a white Christmas!