Cold Frontal Passage Update & Beyond!

We are going to start this update off by talking about the cold frontal passage. Due to the time that this update is being done we will not do a rainfall total map with this update but we will follow this update with a map later on in the day today..

Now you will recall we started talking about this being a cold frontal passage that would be slow to approach the area and that this frontal passage would produce showers and rain and have the potential of some snowflakes on the back side of the frontal passage if there is enough QPF left over. There is no real change in thinking from that which we put out on the 20th of the month.

Models had gone thru there cha cha which some outlets , some of which were pro’s were guilty of jumping on and suggesting that a wave was going to develop along the front and produce heavy snow in locations. Well..those outlets were doing something we are strictly against which is forecasting what they WANT to see happen or giving an opinion instead of a forecast based on the guidance that is available. So lets look at that guidance tonight!

Now the above models as you can see our the ECM and the GFS. These are the two models that we prefer to use for this upcoming cold front.

We are once again going to lean towards the ECM in this forecast with showers moving into the region early Wednesday morning between 8 am and 12 noon. Low pressure should develop off the coast of SNJ which will enhance the rainfall across the region. As for the cold front itself it should approach eastern PA on Thursday evening. Temperatures ahead of this front will probably be in the mid 50-s to low 60s in southern PA up towards NYC. This is WHY this will be a mainly RAIN event..however.. by 2 AM temperatures should be in the 30s in all of PA with the exception of extreme SE PA and central and SNJ . If at this point and time there is any precipitation left over it is possible that snow flakes could mix in with the rain or even just change to some light snow..However..with ground temperatures being so warm..it would not be able to accumulate so most locations IF they do change over would be less then a dusting.

Rainfall expectations with this cold frontal passage are between 1-2 inches.

Now this is where things become a little interesting and once again we are looking out ahead by about 6-7 days.

The cold front moves thru and guidance is beginning to pick up on a piece of energy that is left behind.

GFS keeps this pretty well south and east and virtually has no effect on the region.

It is important to keep in mind two things in regards to the GFS:

1. In this range it has a cold bias

2. In this range it can also have a SE bias

The GFS never really digs the trough that deep so the system stays OTS.

When we turn to the other guidance…

The above is the UKMET and you can see as well how this delivers a system in the southeast and then moves this system up the eastern seaboard.

We turn to the ECM and this to shows the same type of scenario and not as far off the coast as the GFS and it effects the region.

Temperatures on the ECM at 2 PM in the afternoon on the ECM  struggle to get out of the 30s to lower 40s. And the precipitation would probably begin as rain but this one has more potential to change over to snow in the interior regions and perhaps into the I-95 region.

Now we are going to re introduce a tool that we used last year which worked out quite well and that was using the NOGAPS as a tool.

To refresh or to explain to the new fans of R.W.S the model is the most progressive model that there is..However ..we found it is useful..with every storm during the winter last year if the NOGAPS was further west then the rest of the guidance..it was an indication that the guidance was to far east and would readjust west…

Using this tool: lets look at this second potential system:

If this works as it  did last year this is an indication that this second potential system should come closer to the coast in future runs. Why? Because this is such a fast progressive model –reality says it should be showing this further east..but since its not..it raises that red flag.

To sum things up:

Cold front with 1-2 inches of rain to move thru and effect the region in the wed-Thursday night time frame.

Potential 2nd system with rain to snow?

Stay tuned as we keep you informed !