Another Coastal Storm

The past week, model guidance has been hinting back and forth a potential coastal storm. Yes, this is the case Thursday evening, Friday, and through early Saturday. Thankfully though, most of the Tri-State will be spared. At least will be spared a 30 incher blizzard! Despite the (surface) low tracking out to sea, the overall dynamics of this storm/event is rather neat.
Keep in mind, I do believe I have mentioned this is previous posts: a stacked low(a.k.a. vertically tilted trough: Strong developing systems usually tend to tilt with height in the atmosphere. Heights in the troposphere (the part of the atmosphere where 'our' weather occurs) are determined by the temperatures averaging along the troposphere below), which is featured on the maps, where the surface low and upper level low are essentially diagonal to each other downstream (on a map) but are really on top of each other through the atmosphere, equals a strengthening storm system. In this case, the surface low is tracking too far East (in the ocean,) to fully become a stacked low. However, New England will feel the affects of it.

Now, the surface low is showing a track out to sea. It is starved of moisture. However, the upper level low from the Great Lakes will travel South and East (which will hold more moisture compared to the surface low). That is where PHI and parts of New Jersey will receive the snow. Model guidance is not showing anything too impressive in way of snow accumulations in this area. However it does become rather interesting over northeastern New Jersey, NYC, Long Island and southern parts of New England.

Here is the reason why: The upper level low 'digs' (yes, think of it literally but on a HUGE scale) into the Appalachians all while a secondary surface low develops develops off the the Delmarva.  As stated before, the surface low will track off the sea. However, with this in place there is influence from a developing Norlun (instability) trough where the moisture from the sea is drawn back into the convergence bands (convergence of winds) at the surface that will produce clouds = precipitation. Areas of troughs can produce localized heavier, in this case; snow. A Norlun trough in particular are inverted (like a sad face) and extend from northwest from the low at the surface and is located under a cool pool of air in the middle and upper atmospheric levels, which could result in rather heavy bands of precipitation (snowfall). The frustrating part about this storm is trying to focus on where these heavy bands of snow will fall. These bands of snow could produce up to a foot of snow accumulations... A foot of snow over NYC again is a huge deal! The bad part of this is that these bands are localized. The weather models can depict this general feature in the guidance forecast. But even on the highest resolution forecast maps, the QPF (Quantitative/total Precipitation Forecast) can vary and can be difficult to define a snow accumulation forecast for these heavy bands of snow. For now, in northeastern Jersey,eastern New York, and New England be prepared for the worst.

Snow will begin to fall overnight starting in South Jersey, Philadelphia, and spreading North and East and will end towards Saturday. Snowfall totals for Southern and Western New Jersey and Eastern Pennsylvania have been reduced. Total accumulations should be a couple of inches. The onset, snow will stick rather quickly on untreated and not so traveled roads. A Winter Storm Advisory has been posted through portions of Northern and Central Jersey as a precautionary for snow accumulations exceeding five (5) inches. On average, we can expect two to three (2-3) inches of accumulation. Heavier band of snow could cross through the area and accumulations could reach of exceed five (5) inches and reduced visibilities through Friday. The morning commute should be fun :) and the evening commute, especially in northeastern New Jersey and NYC will be a real joy :-D ! The surface low will track quite close to Long Island, so it is possible for LI to see brief change over to rain Friday.
A Winter Storm Watch is still in effect for portions of Northeastern NJ, central and Eastern NY, Long Island, Massachusetts, Connecticut, and Southern Vermont. Snow in these locations could exceed five to seven (5-7) inches. Again, higher snow accumulations, up to ten (10) inches are possible in heavier snow bands.
Generally, we know the track of the storm. But now the real issue is trying to figure out where these heavier snow band will land. Remember, any kind of shift of the coastal low will more or less make or break the storm; meaning some locations could receive more or less snow; as in any case and using precaution is always advised and conditions can and will change through the next 6-12 hours.

Forecast valid 1/6. Courtesy of NWS/NOAA/HPC

Once this system moves out, cold blustery conditions move in with high temps Saturday, as the snow comes to an end, only in the middle 20s! High pressure moves in for the rest of the weekend with mixed skies of sun and clouds and chilling temperatures in the lower 30s as daytime highs falling to the teens in the evening.

It looks like it will feel like an icebox again my friends...

~V.S.