There is so much to talk about this evening that I decided to make one large post and also make this one free because there’s some important thoughts here that need to be covered.  As you can see from the image above, the Polar jet stream is full of pesky disturbances that are targeting the New York City and Philadelphia metropolitan areas that is leading to periods of snow showers.  The change in the pattern is now those disturbances will have a partner in the form of a more active Sub Tropical jet stream, which I’ve been warning Premium Members would become more of an issue for the rest of this month due to Pacific convection developing around the date line.

First I want to touch on the developing snow shows associated with these clippers that are approaching the New York City and Philadelphia metropolitan areas.  For the most part we are dealing with light snow showers with accumulations of a trace to two inches.  The disturbances, especially the one over Michigan, Indiana, and Ohio; are rather robust though and could enhance a snow shower or two to produce a period of moderate to heavy snow for a short period of time between this evening and tomorrow morning.  I wouldn’t be surprised if a brief snow squall sets up with that disturbance over the Ohio River Valley.

Of course the real story or at least what’s on everyone’s mind is the storm for Thursday night into Friday.  I know there are some that are not going to like me saying this, but if you are south of New York City I still don’t think this storm is for you.  However, if you are in northeastern Pennsylvania, northern New Jersey, the Hudson River Valley north of White Plains, and especially Connecticut (and really much of southern New England) your snow drought is potentially coming to an end in a big way.  When I look at the 500 MB pattern, I don’t see the signs for a major snow storm for the Mid Atlantic, New England certainly, but not further south into New York City to Washington DC.  The reason why is simple.  The 500 MB pattern is lacking key features ahead of this storm.  One, the ridge is too far east on Thursday morning thus leading to a more progressive wave length to the east.  Second, there is no high latitude blocking over the Northern Atlantic, specifically a 50/50 upper level low.  This is why a surface high over Quebec, Canada is too far north and east because the upper level convergence aloft (500 MB heights close together on the map) is too far north.  I can go on, but I don’t want to depress you.  All this leads to cold air being driven out of the coastal plain and thus a likely outcome of snow changing over to rain.

However, for points further north and especially over New England, the surface high is still close enough to keep cold air locked in to work with the storm track which in itself is in a favorable location.  While I’m not prepared to forecast for 20 plus inches of snow in Boston, I will say that southern New England, based on the latest data, is setting up for a very impressive snowfall for the region.

Here is how I see this storm play out.

Thursday night into Friday morning, the Polar and Sub Tropical disturbance starts to phase and interact leading to a rapidly intensifying coastal low pressure system around eastern North Carolina or the North Carolina coastal waters.  Precipitation rapidly expands northward, possibly starting as snow even for southern New Jersey as 850 MB temperatures will still be at or slightly below freezing.

Friday afternoon and evening: The low pressure system takes a perfect track over the New Jersey/New York coastal waters.  However, as discussed above the cold air is driven out via an easterly wind ahead of the storm.  This leads to a snow to rain (a rather chilly rain) all of the Philadelphia metropolitan areas, all of coastal New Jersey, New York City, and Long Island.  Snowfall accumulations could push to 4 inches depending on how fast the change over is.  Meanwhile, a mix of snow, sleet, and rain can be expected just north of New York City and on the shore of Connecticut.  Northeastern New Jersey, the southern Hudson Valley, and southern Connecticut will get a mix of snow, sleet, and rain making for a mess on Friday evening rush hour.  Snowfall accumulations over 4 inches is currently expected with the potential for icing being a problem for portions of the southern Hudson Valley and northeastern New Jersey.  Just to the north, all snow can be expected from northeastern Pennsylvania, northwestern New Jersey, the rest of the Hudson Valley, and central and northern Connecticut.  Northeastern Pennsylvania will be on the edge of the steady, heavy snowfall with potential accumulations of 4 to 8 inches, up to 10 inches as you move closer to the Delaware River.  For northwestern New Jersey on through northwestern Connecticut, snowfall totals could exceed a foot of snow based on current data.  Finally, for much of central and northeastern Connecticut, snowfall amounts are expected to be the highest with amounts possibly exceeding a foot and a half of snow.  Of course, all of this can change quickly so we’ll have to watch out how this all works out.

After this storm exits, the pattern will be set up for another storm around February 13-14 will be brewing.  Preliminary data shows a weak 50/50 low will be in place along with plenty of cold air along the coastal plain.  The Sub Tropical Jet Stream will be providing plenty of moisture for this storm and the 500 MB wave lengths would be in perfect position for a potential significant snowfall for all of the Mid Atlantic from Washington DC to Boston, Mass.  Of course, there is a lot of time to see how this all evolves but such a partner shown above would support the largest snowfall seen in over two years.  I know, not saying much but still something to consider.  Looks like I’m going to be pretty busy!