Here is a look at today's 12z EURO 500mb height anomalies valid late Saturday. This is a good look of how the pattern will set up. As explained yesterday, we will have a -NAO/+PNA to work with. The higher heights over and east of Greenland is a nice -NAO. Not classic but it's our best block all winter. The ridging in the west into the Arctic is a very impressive +PNA/-EPO. This is what will help drive the northern energy and arctic air into the northeast. The goal is to get a phase to occur between the northern and southern phases. As shown yesterday, we do not need a phase to get a big snowstorm since the southern energy is strong on its own, but I would feel comfortable knowing a phase will happen because it lessens the odds this storm goes out to sea like the GFS OP is trying to show.
Today's EURO at 500mb is almost a replica of yesterday. There is no phase but the southern energy is stronger today, so the surface low is pulled closer to the coast and those west into PA get into the action. Notice how the northern energy is still over the Great Lakes but it's trying to dig quickly into the coast for a phase.
Recall yesterday the EURO was showing a surface low around 991mb. Now it's closer to the coast and around 988mb. The EURO Ensembles are even more impressive. Some members are around or sub 980mb with the low so close to the coast that the Jersey Shore and Long Island see rain or mixing.
The 200mb jet streaks and wind vectors suggest this storm has a clear path up the coast toward the Benchmark. It will be interesting to see how dynamical this system could get. If there is no phase, the storm may struggle trying to wrap colder air into its core so dynamic cooling would be difficult to achieve. This may bring mixing concerns to parts of the immediate coast, including NYC. Even though the EURO is not showing this, it's still worth noting soundings may be showing a warm layer somewhere. This is why it's critical we at least see a partial phase with the northern energy.
The GFS is off the coast because it rushes the southern stream ahead of the northern stream and the vorticity never wraps itself into the trough. Everything looks a little fast and pretty strung out. It does not have support from its own ensembles nor other guidance such as the SREFS and GGEM. The only reason I am not completely discounting the GFS is because of the northern branch remaining disjointed from the southern one. However, the southern branch should be able to manage a storm at least near the coast given the -NAO/+PNA/-EPO.
Tomorrow will be a critical day of model runs if you're a winter weather enthusiast. Either the EURO holds serve and regains its reputation as "king," or the GFS will out perform it once again like it did a few times this winter. At this moment, I am leaning in favor of the EURO and its Ensembles because I feel it handles -NAO type storms very well. and it has support from other guidance. Therefore, I am currently forecasting a 6 to 12" snowfall for the area beginning midday Sunday into the 1st half of Monday. The potential still exists for a Godzilla (12" or more). We'll see!
Enjoy the rest of your night.
Best,
Francesco Paparatto
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