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Major Storm to Deliver Largest Snowfall of the Year! 3/3

After a long winter of no major storm to track that has finally changed! In March no less! A developing low pressure will strengthen and slide south of the region and will provide the area with a up to a foot of snow in some regions!

Over the past two days models have shifted to the south and east and have moved on to the idea that the heaviest axis of snow will fall along the I-95 corridor. Even the mighty European model was too far northwest and caved to other guidance. We can visualize this with a 500mb map from models over the fast few days. Notice how the lowest heights move from further inland to off the coast.

This storm is going to be a fast mover and with a lack of traffic in the Atlantic Ocean and no rising heights over Greenland this storm is booking it. Here is my scenario 2, from a few days ago depicting what will happen with the system.

This scenario looks nearly identical to what is actually going to occur. Now, lets dive into models and do some analysis.

First off, the storm that impacted the region 2 days ago and delivered 3-5" of snow in some places is really helping us with this current storm.

The storm is acting as a 50/50 low at 50N and 50W and is helping usher in cold enough air for snow as well as providing "some" traffic in the Atlantic to help slow the storm down a bit. Without this low pressure there this storm would have likely been too far north and west for any significant snowfall in the major cities.

I am currently leaning on the higher as well as colder side of guidance for this storm for multiple reasons. First off, models have been continually trending with more and more precipitation leading to higher snowfall totals.

More precipitation generally means more snow! For instance the NAM moved from .5-.75" for New York City to 1-1.25" of precipitation. This also signifies to me the storm will likely be colder and snowier for the coast than what is currently being depicted. Lets check out the latest NAM rain/snow line for later tonight.

The NAM is showing very heavy rain for Long Island and New York city for this specific hour. But we should not take the model at face value, we should look at whats going on above the surface!

A few thousand feet above the surface we can see that there is a pocket of much colder air centered over are as where the model was showing rain. This signifies to me that the precipitation is not actually rain, but snow! The cooler temperatures are due to very heavy snow pulling down colder air. This is a process called dynamic cooling and can be accompanied by snowfall rates exceeding 1" per hour. Models are also showing a lot of lifting in the upper atmosphere at this time which is causing heavy snow to pull cold air down. We can visualize this lifting using the 850mb frontogenesis maps on models.

As you can see the heaviest rates of lifting are centered just along the coast and this is where rates of 1-2" per hour or more will be present. However, what goes up must also come down. Regions that are just north and west of where this lifting sets up will be victims of subsidence and very light snow as all the moisture gets sucked out of the atmosphere into the lifting. Some regions will defiantly underpreform but those within this band are likely to hit the high end of their range or even go over the forecast.

My current model of choice for this event would be the RGEM as I thin it has the correct snowfall axis as well as thermal profile. It gets mixing close but due to the frontogenesis , it keeps it just barley away from coastal areas.

Last but not least, here is my snowfall forecast!

I moved the heaviest totals south and east from yesterday and also added a higher contour to account for heavier totals. I have the heaviest snow being in the eastern half of Connecticut through Rhode Island and just south of Boston. Someone in that region will likely see up to 12" For my 5-8" region I have most of eastern Pennsylvania into northern New Jersey, the lower Hudson Valley and New York City/Long Island. These areas will experience up to 8" and possibly more if banding sets up. If there is a bust area it would be the northern fringe because if banding sets up to the south it will create lighter snow rates. This is my final forecast any questions can be directed to my twitter @mikebweather

Cowan, Levi. “Forecast Models.” Current Storm Information - Tropical Tidbits, 3 Mar. 2019,