Mid Week Storm and Pattern Update ..X Mas Eve Edition!

Let us start this off by wishing each and every one a very merry christmas from Down to Earth Weather forecast center.

We have been off the computer for a little bit of time but we are now back and we are going to be discussing the pattern as well as storm potential for the midweek system. Before we get into that though lets take a look at where we have been...

No doubt it has been a very warm december with temperatures well above normal across not only the Northeast but majority of the country. This is a far cry from what was anticipated to happen for the month of December. We are actually over the next couple days going to be re looking at the winter forecast and chances are pretty substantial that we are going to have to issue a revised outlook. We did this last year and it looks like it may be the case again this year.

So lets look at the guidance with the upcoming storm system and again if you are a snow lover you are going to have to according to the guidance be pretty well north in order to obtain any snow (snow that would be substantial or major) ..

GFS as you can see has the system after initialing bringing some frozen move inland and changes everything over to a cold rain. Now normally we would say "Hey its the GFS"... but truth be told its not alone..

It has support from its ensemble means. But even still the GFS and GFS ensembles are not alone either..

You can see the GGEM as well takes this into south central PA and turns all of the southern half of PA into rain including east central PA and almost all of NJ ..again this is after some initial frozen precipitation.

The UKMET is really not that different from the above models that we just looked at ... 

And as you can tell the NOGAPS is also very similar to the rest of the guidance and would have the frozen precipitation well inland (west and North)...

Last but not least is the ECM 

Here is 78 hours and you can see that even the ECM brings precipitation issues even into the poconos.
So what is the problem we may find ourselves asking. Why is it that we may start as frozen and change over to a cold rain. 
Lets start with the fact that we have not had very much cold air this whole month of December..
Lets take a location like Allentown PA for example where on the 23rd the high temperature was 41 degrees. This is STILL 3 degrees above normal for the high temperature. So while it may APPEAR colder we are still warmer then normal.
Another factor is the teleconnections and this ties into the pattern as well. While it is true that we have the NAO negative...

And while it is true we have the AO negative...

We have two other factors that are working against us. 

The PNA is neutral Negative . Simply what this means is that any storm that tries to come across the country or up from the southeast is going to try and cut because of that negative PNA. 

And we also have a neutral EPO (present ) but at the time of the storm- positive EPO. 
We also are seeing a track that is taking the system literally across Southeast PA and across the NJ coast.  And a interior track like this is never what you want to see for an all snow event. Can this change? Yes ..However..at the present time it would be foolish to forecast an all snow event unless of course you are well north into NY State for example or into Western PA like the Pittsburgh area. 
We do though see some hope when looking at the 850 temperature anomalies and that is we no longer see a Alaskan vortex... However..the teleconnection combination you want to see for a snowstorm as well as a pattern change is for the following teleconnections to occur.
1. A positive PNA
2. A negative NAO (preferably west based)
3. A negative AO 
4. A negative EPO
That is the combination of what you want to see ... that is what you want to keep an eye out on. 

As for this system it looks to be mainly wet then white ...outside of the northern tier of PA and further north. 
Though we do not put much stock or faith into the images this is just to give you an idea of what the ECM sees in a three hour time frame wed evening...

On a brighter term for those winter weather lovers we just may have to wait for the next storm. Since this is like three waves of low pressure over the next 7 days (first one being a minor system and nuisance Christmas eve into early morning Xmas) and then the midweek storm and then perhaps the weekend ahead...

This one would indeed be cold enough for snowfall..However..lets get thru the midweek system before we talk about that one :)