Today's Text Forecast | Public Forecast Discussion | Technical Discussion | Graphical Forecast

It is raining in the Bronx. That's the bad news. The other bad news is the performance of the models today, which has been atrocious both with the positioning and intensity of precipitation. The NAM continues with it's highly dynamic event, but has shifted a good 50-75 miles southeast of it's previous forecast. In fact, it keeps the highest precipitation confined to the New Jersey Shore/Long Island and the southeastern areas of the metro. The GFS, on the other hand, is well northwest of the guidance envelope (and much warmer aloft). It's interesting to note that the GFS was involved in an awful forecast on last nights 00z model run suite, indicating that heavy QPF would be over the metro area by 12z this morning. Obviously, this hasn't happened. The NAM definitely won the precip-timing battle in that regard, but both models seem to be off with the precipitation falling right now..which is relatively light but is definitely coming down at a decent clip. It's nothing the models usually don't pick up on.

The timing differences from last night's models can be attributed to a few key features, displayed on the image to the right. There's a weakening shortwave, which moved northeast out of the trough base last night, over New England. Meanwhile, the more robust shortwave (which will be responsible for touching off the strong dynamic precipitation tonight and tomorrow) is ready to eject northeast out of the trough in the southeast states. Between these two features, the NAM correctly indicated a brief period of mid level ridging (ridge axis drawn in a pink line). The other two features are circled in pink. The mid level ridging acts to provide subsidence to tamper/inhibit the development of stronger/more steady precipitation. The GFS was incorrectly weak with the initial shortwave, weaker with the ridging/subsidence, and brought precipitation into the area a good 8-10 hours too fast.  This is why the precipitation is currently light/spotty...and it will remain that way until PVA (Positive Vorticity Advection) from the second shortwave can overtake that later tonight as a low pressure area forms off the Mid Atlantic coast.

John

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

It's safe, at this point, to say that we've seen the last of the sun for the next few days. An unseasonably deep and anomalous weather pattern will begin to set up later this week across the Eastern United States, impacting our area from Thursday through the end of the weekend, and quite possibly into Monday. All of the ingredients typically needed for a pattern mentioned above are there. The featured image to the left shows the pattern as depicted on the 36 hour 12z Operational GFS forecast at H5. A few select features are noted, beginning with the presence of a large west coast +PNA ridge (A).  This ridge is often responsible for resultant toughing across the Central and Eastern United States. Though the ridge is progressive/transient, heights are forecast to rise well into Western/Central Canada, aiding in the amplification of the trough downstream. A very progressive/weak blocking feature is in place across Eastern Canada/Greenland (B). A feature more typical to an anomalous east coast trough would be a more sustained block, but the presence of the +PNA ridge will tend to "substitute" for this missing block. The result (C) is a mean trough over the Eastern US. The pattern is still "dirty", meaning there are multiple shortwaves embedded within the trough and the forecast guidance is still struggling with the energy, specifically with determining which storm will be the main player and when the impact will occur. This creates havoc on the guidance including difficulties with strength and timing of each system.

The lead system is forecast to emerge out of the base of the trough as seen on the 36 hour forecast, with a surface low pressure traversing through the Middle Atlantic states and eventually off the Mid Atlantic coast. Unseasonably cold temperatures are in place and will be generally held in place as a surface high pressure builds southeastward into Quebec. This really is a mid-winter pattern, and a snow lover's dream. By 00z Friday (Thursday Night) it's reasonable to assume a ~1000mb low pressure system will be organizing off the Mid Atlantic coast and heading northeastward. Forecast soundings are interesting in a couple of ways with this system. First, the dynamics actually get interesting during the height of the system early Friday with modestly favorable omega values/uvv's. Additionally, the soundings indicate a good amount of cold air at the surface to start, indicating northwest interior/mountainous areas/higher elevations may actually begin the system with a short period of sleet or possibly snowflakes. These soundings are somewhat suspect, but the dynamics and cold air to begin with cannot be ignored. The image to the left shows the sounding for KSWF from the 12z NAM valid at 33 hours. It's easy to see how borderline the sounding is, with low level air barely -0.2 C. Still, if taken verbatim (not always the smartest idea) the 12z NAM would indicate a good 4-5 hour period of snowfall at the aforementioned station.

Digesting all of this may be somewhat difficult. The fact is that there is an extended period of precipitation forecast to impact the area (including the metro) over the next few days. It's not likely that snow will fall within the NYC Metro area, but rain amounts could total over 2-3 inches by the time the prolonged period of precipitation ends. Further north and west, especially in mountainous areas and higher elevations, a period of snow and or sleet to begin the storm can not be ruled out. The rain that falls elsewhere will be a raw, cold rain. Not very conducive to baseball, I may add. Some of the forecast models indicate a respite in precipitation Friday evening between systems, so they may possible be able to get in a cold, damp ALCS Game 1.

After this, the trough over the eastern coast becomes even more anomalous and cuts off from the upper level flow. Another coastal low is forecast to form along a boundary just a few hundred miles off of the Mid Atlantic coast. With a second area of vorticity moving northeast up the trough axis (aligned southwest to northeast along the eastern seaboard) this system, again, may be dynamic with areas of enhanced precipitation possible from Eastern Pennsylvania to NW New Jersey and possibly the Metro region eventually moving northeast towards New England. By this time, additional cold air will be filtering southeast from the broad upper level trough, and as such it appears possible that flakes may fall in the mountains of NE PA at this time frame. Really a wild pattern for this time of year: but for us, it adds up to a wet forecast over the weekend with possibly a brief period of white or grey well north and west. We'll have a post on storm number two later tonight with more details and buzzings about the upcoming cold and wet weekend. Take it easy.

Oh, and as an aside: Yes, the blog is fully up and running. Functional, comments and criticisms allowed. We hope you continue reading and leaving us your thoughts and comments on each post. We will continue bringing you our thoughts and information as often as possible, more than likely once a day or once every few days.  

John