**This post is dedicated to Daniel Barden, age 7, a victim of the Connecticut shootings.**
The potential for a winter storm in the Plains and general East US is present between the 26th and the 28th, as the ECMWF is now showing such a potential.
The above image is for the morning of December 25th. We see our system as a deep depression in the Plains, in a 'U' shaped depression. Such a deep depression gives me three clues:
One, this system could be pretty strong when it ejects from the system.
Two, the deep-ness of the depression and neutral tilt tells me it could evolve into a closed low.
Three, a cold air outbreak could follow this system if cold air is available up north.
That ridge present in the eastern US displays a sort of positive PNA feel, with the typical positive PNA ridge on the West Coast also in play. This looks to be a Midwest/Plains storm transitioning to the coast, where the Mid-Atlantic and Northeast may be affected. No guarantees, however.
This is the Hour 240 forecast from the ECMWF, once again dealing with 500mb heights. We see that the storm system has now evolved into a very deep closed low, meaning it has been cut off from the jet stream. Closed lows are notorious for staying in place for days on end, but this does not look like it will happen. We have the system squeezed in between two high pressure systems. One is in New England, prohibiting the storm from going directly northeast, and the other ridge is in the Rockies. Considering the ridge in the Rockies looks much stronger, and the angle of the ridge favors a direct east path, I do not find the idea of the Midwest, Ohio Valley and Northeast getting a winter storm totally off the table. This closed low would indeed bring in a lot of cold air to the Midwest and Great Lakes.
The ECMWF also shows a very nice accumulation of snow in the Midwest from this system on the 26th, shown as the colored values above the dark blue 32 degree temperature line:
And the very high amounts of precipitation in the Mid-Atlantic some time later on Dec. 27 tell a possible severe weather story:
All in all, it's looking pretty interesting. While we are still a while away, we are in a negative PNA pattern favorable for an amplified storm track. If a steep negative NAO evolves, we could have a highly meridional flow more conducive for strong storms.