Models Coming Into Agreement..But Not All!

Models are actually coming into better agreement on the upcoming storm system across the east between the 12-14th of December.

What originally started off in the models about a week or so back has changed dramatically. We have gone from a Nor Easter type system to a anafrontal system which may transfer to a secondary somewhere along the east coast between Hatteras and Delmarva. Normally this type of system would provide snowfall to parts of the region ..however..majority of the modeling is in agreement on the primary becoming pretty strong and heading towards the Great Lakes region. What this does is set up a strong flow of WAA or Warm Air Advection so temperatures at 850 rise ..and temperatures at the surface rise. Cold front makes its way eastward ..however..cold air makes it back in the area to late to prevent rain from happening.

So lets look at the modeling and we will see the agreement that is there tonight…

Now as you can see the models from top to bottom..ECM,GFS & UKMET are all in agreement at 72 hours and they all show the scenario discussed up above. So we have good agreement and the means essentially support the operational runs.

However..we have two other pieces of guidance that stand out.

Both the NAM & GGEM show a secondary along the coast or another low that pops up. On the NAM this pops up after the cold front has started to go thru the area, Now the 6 Z NAM continued this trend as well so it will be something that has to be watched to see if the other models pick up on this or if these two models are just going to be outliers.

So here is how I think this will lay out at this point and time. Primary will head up towards the Great Lakes region and develop a secondary. Meanwhile the cold front will be working its way off to the east. Essentially its a race between the cold front and the secondary. If the cold front can cross the region before the secondary arrives then we could be looking at a more interesting scenario. However..if the cold front is slower then this system is going to produce rainfall on its eastern side. SE NY, Eastern PA, SE PA, all of NJ ..potentially even Central NY and into New England.

Now there are a few things we need to keep an eye on.

1. Do other models start to pick up on the same low pressure the NAM develops?

2. Lower Level Cold Air..Does it erode as quickly? Or does it hang tougher?

3. Keep an eye for a weaker primary..A weaker primary would mean a less surge of WAA

4. If a secondary develops, where does it develop and does it become stronger then the primary?

At this point and time a Level 1 may need to be upgraded to a level 2 for the western and central parts of PA, western NY and All of Ohio. This will probably be done later today when I issue a preliminary scenario map.

Stay tuned for further updates on this developing storm!