The energizer bunny winter continues, with yet another winter storm set to impact the Northeast US mid week. Over the past month, NYC has received 56.1″ of snow, an unbelievable amount, and double the snow we’d usually see in 2 winter seasons combined! This upcoming storm will not be a snowy one for the metro area as the synoptics are not conducive; however, it could very well be an icy outcome, and here’s why…

Note the following 00z NAM H5 depiction valid Tuesday. Very little blocking is in place downstream in the NAO region, allowing the SE-ridge to flex its muscle and thus the incoming short wave cuts further NW than most of our storms so far this winter. No Greenland block means the baroclinic zone lifts well northward, especially in a strong la nina year. However, there is strong confluence present from the Mid-west to the northeast, with surface high pressure extending W-E in a classic “banana high” fashion. High pressure pressing down the Plains could reach 1050 to even 1060mb based upon some data!

What does this mean for our local area? Well, the track of the low is likely to move NE into the Ohio Valley, before running into the surface highs and transferring its energy across PA-NJ, then offshore. So the mid/upper level flow will be SWLY/SLY and supportive of rapidly warming 850mb temperatures. Translation — any snow accumulation should be minor w/ this event, and occur w/ the intial wave of precip Tuesday morning. We’ll see a break from Tuesday afternoon into the early overnight, before the main event arrives late Tuesday night through Wednesday midday.

This is when it gets interestings. High pressure will be holding strong over SE Canada w/ a NELY flow at the lowest levels of the atmosphere. Consequently, freezing rain is good bet for virtually everyone Tuesday night into Wednesday morning. When we change to plain rain, that is, IF we do at all, is the big question in my mind.

Note the 00z NAM sounding for Wed morning 12z in NYC. Follow the 0c line down diagonally. The red and black lines indicate the temperature and dew point respectively. Temps are above freezing between 800-900mb, but then fall back sub 32F in the lowest 100mb of the atmosphere, favorable for freezing rain.

By the time NYC changes to rain on the 00z NAM, precip is almost over.

If we examine model trends over the past 24 hours, there’s been a clear correction warmer in the mid levels but colder at the surface, which makes sense given the synoptics and strong high pressure to our north. What this means, at least locally in the NYC metro, is there’s likely to be less snow than currently forecast, but more ice accural. The NAM prints out about 0.5″ of precip as freezing rain (ice) for NYC, which includes most of NJ and LI as well.

My concern is we’re not finished with the trend towards a colder surface, as we’re still 48 hours away from the event. Given the trends recently and the set-up, the potential exists for a significant to damaging ice storm across much of E PA, and interior N/C NJ. A significant ice storm may also occur right down to NYC and the coast. Keep an eye on this situation closely, as an ice storm could be destructive with the already deep snow pack on the ground and buildings in the area.