What's the deal with the Sunday/Monday Snow???

I would like to start off by saying this has been one of the most complicated, complex, and confusing forecasts I have at least ever attempted and I'm sure many who forecast as well, whether they be meteorologists, aspiring meteorologists, or hobbyists, I'm sure would feel the same way.  The degree of model uncertainty, the lack of run-to-run consistency, and the lack of model agreement has been jaw dropping.  While this is extremely frustrating for forecasters, the most frustrating aspect of the situation is trying to inform the public.  Unfortunately many in the public eye don't understand exactly how challenging weather forecasting can be and what goes into composing a forecast.  While its completely understandable how everyone would like exacts, unfortunately there are times in the forecasting industry where you can't really be exact and that's just the nature of the beast.  What I would like to do is begin with trying to explain and show why this forecast is so challenging and extremely low forecast and hopefully this will at least give the public an idea as to why it seems like meteorologists don't really know what will happen.

What I would like to show first is a graphic from one of the computer forecasts models called the "SREF" (short-range ensemble forecast).  The SREF is an incredibly useful tool as it is composed of various members which each suggest a potential solution as well as showing a mean of all the members.  When there is very little spread within the members (meaning there is great consistency with all solutions) this typically leads to a higher than normal forecast confidence.  On the other hand, where there is a greater deal of spread, this leads to a lower than normal forecast confidence.  The image below is from today's 15z run (meaning it was initialized at 11:00 AM EDT) and centered at Windsor Locks, CT (BDL).  This particular graphic is showing projected snowfall totals.  Each of the different colored lines represents the various members which compose of the SREF.  Notice how the range is from 0'' all the way up to 12'' and notice how far apart each of the members are:

 
This degree of spread this close to an event is UNREAL.  Typically in some situations it is a good idea to just take the mean of the spread but that may not really be ideal here.  If we look at each individual member, there seems to be a greater clustering between like 0'' to 4''.  The mean (the solid black line) is right up around 5-6''.  It is possible this is being skewed slightly due to several members spitting out as much as 8-12'' of snow.

Let's also look at the past runs of two of the American forecast models, the NAM and the GFS.  We will look at this mornings runs as well as this afternoon to illustrate the inconsistencies.  The displayed graphics are showing sea-level pressure (SLP) along with 3-HR precipitation accumulations.  Just look at each model has shifted in just 6-hours with regards to track and intensity of the precipitation (the yellows indicate moderate to heavy precipitation):

It is these differences, these inconsistencies, and these changes which have led to all the confusion and low confidence forecasts.  The major problem is all major sets of computer forecast guidance has continued to waiver back and forth and with that happening there is really no way to even decide which model to perhaps favor or lean on.

Hopefully this little bit of insight has perhaps clarified why this forecast is so challenging and why forecasts for this event keep on changing.  With this said, it is now time for me to make my very best educated guess, using as much science and knowledge as I have in order to compose some sort of forecast.  In composing this forecast I realize the likelihood of being wrong and busting (either too low or too high) is more likely than not and if that does occur all you can do is hope you learned as much as possible.

The forecast:

1) There are ingredients on the table which could allow for a bigger storm to happen.  We have a nice ridge out in the western United States with a deepening trough here in the east coast.  We have some shortwave energy rounding the base of the trough as well as a piece of energy pushing in from the northwest.  We also have a trough which appears to be trying to become negatively tilted (which is something we need for a storm to become stronger and also track closer to the coast):

2) This may or may not play a role, however, in my opinion I think it can but sea-surface temperatures off the coast are quite warm, in fact much above-average.  If the system tracks over these warmer waters, this will intensify the low-level temperature gradient and supply ample moisture.  This would certainly allow for rapid storm intensification and would mean some major snowfall amounts somewhere:

 With the latest set of guidance coming west, this would allow for some very intense lift to traverse the region which would mean a very intense banding of snowfall occurring across a narrow zone with high snowfall rates (up to 2'' per hour).  I will post a bufkit profile from Windsor Locks, CT (BDL) showing how even some models would suggest a period of intense snows back into central CT at least.  Bufkit profiles for other areas across southern New England are also suggestive of this.  The yellow contoured lines (which is what the "snow growth" arrow is pointing too) shows which level of the atmosphere is prime for the development of dendrites.  You would like this zone to between 12,000 and 18,000ft and that's exactly what we have here.  The omega values (where the omega arrow is pointing at) measures atmospheric lift.  Red values indicate upward motion (needed for generation of clouds and precipitation) and blue values indicate downward motion (inhibiting development of clouds and precipitation).  If you're looking for precip (and heavy precip) you want red values within the best snow growth zone the more negative the values, the more intense the precip will likely be (the red values are measured in negative values).  In this particular sounding we see -15 units of omega which would indicate at least a period of moderate to heavy snow:

 
Given what I have said above, I do think we will see a rather impressive coastal transpire and develop and it will be close enough to the coast to provide some impressive spring-time snowfall totals, especially the further east you go.  I do not have much confidence in this forecast, however, the ingredients are on the table for a major event and it will not take much for that to occur and seeing some of the latest models make a big shift west leads me to believe that potential is still very much in play.

I would expect snow to come down moderate to heavy at times, beginning perhaps early to mid Sunday evening (maybe some flurries earlier in the day) and intensifying as we move into the overnight hours.  During the peak intensity, some areas could see snowfall rates upwards of 2'' possible along with the potential for thundersnow which could locally enhance snowfall rates even further.  Winds could become quite gusty as well and could lead to some power outages.  The snow should last through late Monday morning so expect very hazardous travel for the Monday morning commute.

Again this is very low confidence and HOPEFULLY either later tonight and come tomorrow morning the models will all converge on one solution, one track and a more confident forecast can be made.