A potent ice and snow storm effected the northeast today. Parts of Long Island are going to end up between the 5-8" range while most of the area will receive 3-6". Central and coastal NJ are seeing quite a bit of ice - over 1/4" reported in some spots - which is making driving conditions treacherous. Power outages are popping up across NJ with numerous accidents also confirmed. Please take it slow on the roads tomorrow morning. One of the reasons why my final call snow map included a "jackpot" area of 4-7" of snow across NNJ - NYC - north shore of LI - southern CT for this storm was because of the qpf outputs the high-res short range models were showing. Further investigating showed that frontogenesis was pretty strong over areas north of the baroclinic zone which happened to set up across central NJ. There was also an H5 ULL swinging across the region which helped enhance precipitation. While some areas did not do so great in PA, this was still a great storm and a fun one to track.
Tuesday Ice to Rain Storm
Today's system is going to deepen over Nova Scotia into a cyclone. Once it phases with the mid-level trough in eastern Canada, that will help usher in very cold temps. into our area Monday night. Low's are expected to get down into the teens. Another mid-level trough is going to drop into the upper Midwest by Tuesday night. Ahead of it, there will be a surface low pressure system that cuts into the Great Lakes. Due to the arctic air mass left behind from today's system, precipitation Tuesday afternoon may start as snow before quickly changing to ice then plain rain. Low-level cold has been poorly advertised on the models this year so I do feel a widespread region from PA to NJ/NY will see an extensive period of sleet & freezing rain.
The GFS at 7pm Tuesday is showing a sub 1000mb low cutting into the G/L with a warm front approaching the area. Before the front gets here and brings us temps in the 40's with rain, the initial batch of precip. will fall as snow or ice.
The RGEM is also showing wintry precipitation overspreading the region Tuesday afternoon before the changeover to rain. I think a solid .10-.25" of ice is possible for most of PA into NY-NJ (including NYC). Coastal NJ and LI I think should be ok and see mainly plain rain. Their surface temps. are expected to be warmer. I would not be surprised though if that changes on future guidance given the low-level cold.
Wednesday Night Into Thursday Morning Godzilla?
The system during this time frame has Godzilla potential - meaning it has a high ceiling to produce snow amounts greater than 12". This does not mean it will, however. This is a very tricky set-up and one that also has high bust potential.
Once again, we will not be dealing with a well-defined surface low. Instead, this is likely to be an overrunning event caused by strong southwest winds coming out of the southeast and helping to bring up Gulf moisture. The Tuesday night storm is going to leave behind a cold front draped along the east coast. A mid-level trough is going to drop into the upper Midwest on Wednesday containing very potent upper air energy at its base.
Ahead of the positively tilted trough is our stalled cold front along with some mild air over the east coast. The trough itself will not only help enhance precipitation along the coast due to the potency of the H5 vorts, but it will also bring with it an arctic air mass. Once these two features combine, that should result in a very weak surface low to develop with plenty of Gulf moisture to work with and possibly stream into our area.
The 250mb level jet streak being advertised is also impressive and positioned favorably to bring about intense dynamics. What will be key is determining the timing of when the cold air reaches the coast. It's very possible that most of us start as rain Wednesday night then transition over to snow by Thursday morning. This is most likely from NYC and points south. It is worth noting the EPS and GEFS have been very bullish with this overrunning event. Some members are showing well over 12" of snow in some spots.
Given the factors outlined above, I am beginning to feel strongly that someone will see a significant snowfall out of this. Whether it's the coastal Mid-Atlantic or the Northeast remains to be seen. Latest guidance is starting to indicate overrunning getting as far west as State College, PA and spreading east into our area with temps crashing into the teens. If this is the case, we'll see a significant snow event.
What to watch for:
1. Timing with the mid-level trough for when it reaches the east coast (hopefully not too late!)
2. Timing of the cold air (also hopefully not too late!)
3. Positioning of the H25 jet streak
4. Intensity of the PVA embedded within the trough
I believe those 4 factors are essential to how this system plays out.
We'll see what happens!
-Francesco Paparatto
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