After a long stretch of no snow in the Northeast mother nature looks to be finally making up for what has so far been a boring winter. Multiple snow events have already impacted the region this week and this storm looks to be the worst of them all.....so far.
A high impact winter storm is beginning to take shape right now across the middle of the country. A low pressure is slowly gaining strength and is going to cut west of the region, but not before a pesky high pressure is able to supply us with enough cold air to throw snow and ice into the Northeast before warmer temperatures trump it.
Over the past day models have been much more adamant bringing higher totals north near New York City. As of right now I am skeptical of this as dry air may be a large problem to overcome especially at the very onset of the storm. With a high pressure situated right over the northern Mid-Atlantic supplying cold air to turn rain to snow and ice, it also lowers dew points. In order for precipitation to start dew points have to be nearly equal to the temperature and high pressures, especially right overhead, make that feat difficult. I attached an image of the NAM mesoscale model to show the the blue is is directly located over us.
It is very hard to be able to get the atmosphere saturated with a strong high pressure refusing to budge. Now the high pressure will eventually slide east but once that happens our cold air pipe shuts off. It is going to be difficult to have the high pressure supply enough cold to keep areas on edge cold for a while, while not being too strong that it dries up the storm and creates virga. This is just one of the few warning signs I see with this event.
Another warning sign that totals may be on the lower end of the forecast is that so far this year models have severely underestimated the amount of mid level warming in the atmosphere, especially with events similar to this. If that was to occur there would likely be much more sleet and plain rain then any snow across the area and that is a real possibility. Bringing that up it is important to remember to not look at just the higher number but to take it as a range where the lower end is a real possibility as well. At the end of this blog I attached my forecast and I stress to look at the lower end of the number ranges because if the atmosphere warms too quickly snow will shut off sooner than anticipated.
Many models today have been trending north with our 700-850mb frontogenesis banding. Banding will set up around Washington D.C. and make it's way north throughout the day on Wednesday. The million dollar question is how far north does the band make it before it dies out. The high pressure to the north of the region will keep most north of New York City out of the worst of the snowfall due to the drier air however models have been slowly creeping it further north with time. Here is a trend of the NAM model for the banding in and around New York City.
As you can see banding has gotten stronger and pushed further north with time. The NAM usual overdoes banding however this is just an example.
Finally we can now look at my forecast. First up I have my precipitation type forecast which will show who is going to get what type of precipitation.
In the dark blue and red I think the is the extent of where the heaviest snow is. Specifically for the dark blue there will be heavy snow. After the frontogenesis band comes through it will change to a light ice, maybe a quick glaze at most, before going over to a plain rain, washing away any thought of winter. In the red I believe heavy snow will be evident however, since that area is away from the coast I believe the cold air will hang on a little longer. This will create some icing problems and scattered power outages especially if icing comes right after the heaviest snow. In the pink and light blue areas I think banding will die before those areas can reap the snowfall benefits of it. In the light blue I do not think ice will be much of an issue as right after the first shot of some right snow comes through the atmosphere will warm enough to change most of that region over to plain rain. In think pink cold air will be evident enough to cause some icing issues even if snow is not really a player there. If anything I expect these areas may shift north over the next day but I currently like where I stand.
Next up is my snowfall forecast. Remember not to just look at the highest number but to take it at a range.
I have a large swath of 3-5" extending most of Pennsylvania besides the extreme northern part of the state. I have western New Jersey in that area as well. If mid level warming holds off a bit more there is certainly the potential for some 6-7" reports but I currently do not foresee that. Philadelphia is right on the line and I currently like 2-4" for them before some ice and rain. For the rest of New Jersey, New York City, Long Island and the lower Hudson Valley I see 1-3" of snow. If banding does not die as fast as modeling shows there is a possibility that some areas slightly overpreform. also have 1-3" north of Boston because there will be enough cold air to work with in parts of New England to reintroduce higher totals. For the rest of the area I have a coating to one inch of snowfall because they are stuck in the middle. They have too much cold air so it kills off the banding but not enough to keep them all snow as the storm moves north.