Once it starts snowing around 12:30-1:30pm around NYC (some of what you see on radar is virga) it is probably not going to stop until Sunday morning. That said, I think this storm comes in 2 rounds. Round #1 is what we we'll see during the day today and is just now entering our area. Round #2 is when I think the fun starts later this evening. That is when I believe we'll see snowfall rates of 1"-2" an hour as warm air surges northward and clashes with the arctic air mass overhead. This is going to produce insane 700mb lift.
Here is 12z GFS H7 VV's around 1pm (round #1)
Here is 7pm (round #2)
By 7pm, this is when we have to start watching for snow changing to ice or rain along the coastal plain. This includes NYC. However, those who are able to remain all snow just west of NYC where the VV's are at their highest will be the jackpot of this storm.
The HRRR model is showing the heaviest snowfall occurring between 6-10pm this evening before the changeover to rain.
Notice where the heaviest snow of 30+ dbz banding is setting up. Just north of the baroclinic zone.
With that being said, this is where I expect the heaviest banding to set up tonight. While my snow map says 3-6" for this area (exception western NJ), I think 6+ amounts are likely IF the banding sets up the way I think.
Another thing we have to keep tabs on today is how quickly 925mb temps warm up. Currently, they are still plenty cold for the area.
Models, however, insist they warm dramatically by this evening once the weak surface low tracks to our N&W. My argument by this point though is how much precip will there be left to work with by tonight? I think the damage will have already been done.
Some folks are already snowing. Otherwise, game time is about 30-60 minutes away.
Enjoy the storm and stay safe!
-Frank
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