The above is what I have been waiting for. For the purpose of this discussion will not be using the GFS.
Currently over the midwest, once again we have energy that is digging down to the southeast.You can see this piece of energy just to the south of Iowa at the time the 12 Z ECM was initialized. Steering currents are pretty much set up to keep this S/W diving along to the SE. You can see this pretty much when you look at the visible satellite as well.
At 24 hours out...the energy is essentially in the Southeast part of the USA around Louisianna. The digging of this S/W causes a strong trough to be carved out over the east and a -EPO ridge to form in the west. The position of the through ATM is a little further to the east then what it was yesterday! This will cause the low pressure to form a little further off the coast of Hatteras then it did with wave #1. You can see the pressure falls already off the coast as things are beginning to gel together.
The Upper level low over the Southeast is going to pull the coastal back towards the coast. Also helping in this process will be the high pressure out in the atlantic flexing its muscles and pushing this coastal low towards the coast as well. You can see this occurring between 24 and 48 hours on the ECM..
Now...to the Northeast of this coastal low we have a 50/50 low in place. We also have a high pressure area to the north of the coastal. IF this were winter time you would have the main ingredients in place for a major east coast snowstorm. The pressure gradient between the high pressure and the coastal low will produce some strong gusty winds in particular along the coast.
The 850s are cold enough to support snowfall on the ECM. I do not think that there is any question about that. At 48 hours the high pressure is located to the north of the system. By 72 hours this high pressure pulls off to the NE..However...judging by where it is at 72 hours for the duration of this event it appears as if it would be to the north of the system.
So the question basically boils down to surface temperatures. I think the GFS is too warm because it has the low pressure system further north then any other guidance and therefore is considered an outlier. The NAM is actually coming in colder then what it originally was as the NAM is starting to shift the low pressure further to the south then what its prior runs were. Basically high temperatures for this storm should be in the 30s to 40s. Pretty much essentially what they were with wave #1. This is going to end up being more of an actual COASTAL storm which means that it will not spread moisture all that far to the west .I believe there will be a tight gradient when it comes to the moisture with this system. I also believe that this is going to be a smaller system..hence a tighter system and more dynamical system then wave #1.
With 850s cold enough to produce snow and marginal surface temperatures and a NE wind I believe that we should be able to see areas of dynamical cooling and evaporational cooling. Once precipitation starts this should help to drag colder air towards the surface.
I do not think that it will be enough though for the coastal areas where this will be a primary rain event. However..i do think that there is a possibility at some point and time during this coastal storm that snowflakes could get into the rain. Snow will basically be confined to the higher elevations in interior sections. Depending on how strong this coastal can strengthen will determine whether we can get enough cold air down to the surface to see any snowfall closer to the big cities or even in the big cities. If this were to occur i think the better chance for it to happen would be Philadelphia, rather then NYC due to the marine influence around the NYC area. However...I am not ruling out some flakes possible even in NYC.
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