Monday, December 17, 2012

December 26-28 Potential Winter Storm

**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.



Armando said...

O wow Andrew glad to see a post for that storm! I just posted on the most previous post about the blizzard, funny because I asked if you could make an updated post about the 26-28 storm so thanks. So could you give me your opinion on if this storm could come up the coast or even transition and deliver my area(north NJ) snow? I know it's early, but in general could this affect the mid atlantic/coast? Thanks!

Anonymous said...

When you say "sever weather" for the northeast and mid-atlantic, do you mean a sever winter storm or just really heave rain. Where do you see the rain and snow line?

Thanks Andrew!

Anonymous said...

Andrew, all the local forecaster keep saying rain, rain, rain here in Massachusetts! It is so frustrating ! Any hope here? They did talk about a pattern change, none! Just the same old same old! Your thoughts?

eddie said...

will there be (measurable) snow in detroit for either of these systems

Alex said...

Awesome post!

Hopefully everyhting plays out the way it should.

Whats up with the rex block? Some other blogs amd forums have been pointing out that there is a potential rex block but the models are weakening it to quickly, therfore bringing it inland mif the rex block is there, the system will track eastward.


Anonymous said...

When will philly get some snow?

Anonymous said...

Hey andrew, Is ohio in the mix for good amount of snow with this massive storm? Thanks.

Storm-Chaser Wx said...

GFS latest Model run takes this LP System into chicago at 984 millibars, but the ECMWF wants to send it to the south, and then probably up the east coast. its still a good ten days away, but some sites are already talking about another blizzard for the Upper Midwest. also instant weather maps gives us another 6-10 inches out of this system as well, your thoughts?

Anonymous said...

Hey andrew. wonderful job. always. my first look is always ur site u (almost:))never lose focus of the facts.
keep it up, (but PLEASE deliver us some snow in SE new york).
now something somewhat off topic. id like ur recommendation of a few good books/websites to read on weather in general and forcasting so i should be able to follow all terminology. thanks in advance. (sorry for posting here but i figured u wouldn't mind).