Potential Exists For A Moderate To Perhaps Major Snowstorm Feb 19-20th- But Where?

We feel the above title is most fitting that for the end of the weekend that a moderate to perhaps Major Snowstorm could occur but the question that needs to be answered is what region is going to benefit from this system. Will it be the Mid Atlantic and Northern Mid Atlantic or will it be the Northern Mid Atlantic and the Northeast…or will this simply go off the coast of Hatteras and out to sea. All these have been shown on model solutions over the past few days.

The exact track of this system is still up in there air on the latest guidance and we are going to take a look at that in operational model form as well as ensemble model form..However before we do that lets take a look at the teleconnections that are in place..

For starters lets look at the MJO or the Madden Julian Oscillation.

The above images tell us that we are in phase 1 of the MJO and the bottom image is the 500 mb temp anomalies and you can see that across the east it represents more in the way of seasonal weather.

The above is the Arctic Oscillation and normally you want to see this teleconnection with showing in a negative direction . However, what this shows is a positive AO …but around the time of the storm this dips to neutral. What this means is that there should be seasonably cold air around at the time of the storm. However..nothing that would be considered arctic cold and that should not be too surprising considering how mild this winter has been.

The PNA or Pacific North American Oscillation looks to be positive and looks to stay positive thru the duration of the time frame in discussion. So this is a favorable teleconnection for trying to get a storm up the eastern seaboard..

Generally what a + PNA will do is set up ridging into the west coast , sometimes into western Canada and then form a trough along the east. So what this teleconnection suggests is that we will have a trough along the east in this time frame.

Now, here is the North Atlantic Oscillation or the NAO and interestingly enough this teleconnection more or less supports a system that would be further north and west.

Generally when storms end up being suppressed it is due to two main reasons teleconnection wise:

A. The NAO is strongly negative which creates very strong confluence over the east/ northeast

B, In tandem with this the AO is strongly negative which tends to help shear or dampen and crush the systems to the south of the Mid Atlantic Northeast region.

Notice we do not have either of those occurring at the present time with the upcoming system.

So in summary of the teleconnections we have the following:

A. MJO Phase 1 favorable

B. PNA positive which is favorable

C. AO which is positive dropping to neutral which is not the greatest but not the worse it just means that this will be a stale air mass over the region instead of fresh arctic supply..

D. The NAO . The NAO being positive argues for more of a NW track closer to the coast…not necessarily to the benchmark but indeed a further NW track .

So now lets look at the guidance and the ensemble guidance and see what solutions if any hold up to what the teleconnections suggest..

This is the 00z GGEM. While this has made a shift to the NW over all…this model is mainly a brush to the northern Mid Atlantic area..with the main storm occurring south of the Mason Dixon line. However..you will notice that this model also is about 12 hrs. slower then the rest of guidance so we will consider this a unlikely solution due to timing issue compared to other guidance.

The above is the 00z UKMET and this is similar in its depiction at least where it ends up at 96 hrs. as the GGEM but it is 12 hrs. faster then the GGEM. This also lines up fairly well with the ensemble means of both the GFS and ECM as you will see.

This is the GFS..this is the operational run and as you can see thus far it is pretty much the furthest NW of any model and the reason why is because it phases in the northern het stream disturbance with the southern stream SW over the southeast. This run is also colder then previous runs because it is not as AMPED up compared to other solutions..

00z ECM is very similar to the GFS in low position ( a little south) however the 00z ECM has taken a major trend with the northern stream disturbance towards the GFS which can be seen in the first 24-30 hrs. of the 00z ECM.

Verbatim about .37 gets to KPHL and only .07 at ABE and NYC..However this is greater QPF then the 12 Z run. Also important to keep in mind is the 12 Z means were more amped and north of the op yesterday afternoon.

So now we are going to look at the three models GGEM/GFS /ECM in the form of the ensembles at 96 hrs..

Now the last image is the GGEM means and you will notice that the means are Southeast..however you will also notice that they are about 12 hrs. faster then the OP GGEM. We are considering these means of the GGEM as lower probability because the model is clearly struggling with timing issues as evident in the difference between the OP and means.

Now the top image is the GFS and the middle is the ECM ensemble means and you can see that they are in fairly well agreement. The main difference is that the ECM is more AMPED then the GFS ..Which is kind of interesting considering the ECM means is a smoothed version of 51 members versus the GFS 12 members. The means of the ECM are also slightly more North as well compared to 12 Z ECM means.

In Summary the teleconnections would support more of a NW track up along the coast with the NAO positive and the PNA positive ..

We do not think the teleonnections are supportive of a system that would be south and east and miss the region..but the ultimate outcome will depend on Phase or no phase of the two streams..If there is no phase then it is very possible that this ends up being a Mid Atlantic storm with nothing but clouds north of the Mason Dixon line.. as it would slide ENE from the Hatteras Area..

If we have a full phase then we could be looking at more of an inland solution because of the positive NAO. With no blocking in place (other then temp block from the 50/50 low) this would then become a primarily rain maker for the big cities along the coast with heavier snows inland..

So there are a lot of questions to be answered yet ..but right now we are leaning towards the following scenario based on the ensemble means and teleconnections..

This much we will say…if this storm does come up the coast in a more northerly fashion that the surface temperatures will be in the low to mid 30s but the 850s supportive of snow. What this means is this would be a heavy wet low liquid to ratio snow and if this does come to fruition then it could become not only travel problems but also problems with trees and wires down due to the snow being heavy and wet..

So the potential is on the table but the exact track is in the air yet and whether we phase or partial or no phase at all.

Stay tuned we will continue to monitor and follow this potential winter weather event!