In what some may consider a great sign for the upcoming winter, heavy precipitation continues to move through the New York City Metro area this afternoon and evening. The low pressure area organizing off the Mid Atlantic coast is largely responsible. Our post yesterday discussed the ingredients attributing to today's storm system. A large, anomalous trough will continue to build into the Eastern US today and into this weekend while a positive PNA induced ridge on the west coast (and associated rising heights) attributes to lower heights and a sharper trough in the east. A strong high pressure system in southeast Canada is responsible for the first flakes which many in the interior/northwest areas experienced this morning. Low and mid level warming in association with the low level jet/warm air pushing northward has turned most areas over to a cold rain at this hour.

Precipitation is expected to continue well into the afternoon and evening, and into the overnight hours tonight. In fact, an area of enhanced dynamic precipitation is forecast to approach the metro area later this evening. Rainfall rates may become locally heavy and flooding will become a concern as the heavier rain is falling. In fact, the National Weather Service has issued a Coastal Flood Warning for some locations. The steadier precipitation is forecast to exit the region by Friday afternoon (possibly in time for Game 1 of the ALCS) though the weather will remain cold, raw, and damp with drizzle likely throughout the area. The forecast then turns interesting again by Sunday. A strong vorticity max will move northeast up the base of the increasingly sharp trough along the eastern seaboard. Forecast guidance has begun to key in on an area of low pressure developing on a frontal boundary left behind along the Mid Atlantic coast. As is normally the case with these intense areas of energy aloft, rather intense dynamics aloft can translate to the surface in heavy precipitation. This means heavier cold rain for much of the area, but for portions of Northwest New Jersey and the higher elevations of Southern NY, CT, and Eastern PA, the forecast could get interesting.

Forecast soundings from the 12z NAM show the feature very well with intense precipitation and high QPF/precipitation totals. With cold air already in place, and additional cold air filtering in from the northwest in association with the upper level trough, the intense precipitation and associated dynamic cooling could cool off temperatures enough to support snow in the aforementioned locales. This would definitely be, in the higher elevations and mentioned northwest/interior areas, a scenario where the heavier precipitation falls as snow and the lighter precipitation falls as rain as a result of lesser dynamics. The 12z NAM soundings for interior areas show the temperature around 2.5 C today (Thursday) but rapidly cooling to near 0c during the heavier precipitation tomorrow. By Thursday Night, the 12z NAM indicates moderate snow falling across these areas (we used KSWF Newburgh, NY as an example) with sufficient snowgrowth and likely some light accumulations. Really just an incredible sounding to be looking at in our general area for this time of year.

As far as the sensible forecast goes, moderate rain will continue this afternoon and evening, heavy at times, possibly mixing with flakes north and west..especially at elevations above 500 ft. The rain may taper off by Friday Morning and Friday afternoon but is then expected to pick back up Saturday and Saturday Night into Sunday with heavier precipitation across certain areas. Again, areas north and west and higher elevations may mix with snow with some light accumulations possible. Overall, as we mentioned yesterday, a dreary forecast this weekend with raw and wet weather expected. We'll have more later, take it easy guys.

John