NY NJ PA Weather Forecasts

Mesoscale features and the rainfall tonight

9:23 AM

I’m going to break up this morning’s coverage in two posts.  This one will focus on the next 48 hours given all the concern about weather impacts for this evening’s ALCS game.

This morning, a strong cold front is currently pressing to the east at a rather slow pace.  The cold front is currently over western New York and western Pennsylvania.  Areas of heavy rain and embedded thunderstorms are currently training over central Pennsylvania and scattered showers are developing over the Delaware River Valley.  All precipitation is racing from south to north ahead of an upper level trough that is in the process of tilting into a negative axis.  The pressure gradient over the Mid Atlantic is due to the strong low pressure over the Great Lakes and the stubborn high pressure system located over the Canadian Maritimes.

The water vapor satellite image this morning clearly shows that an abundant amount of moisture is being pulled northward from the Gulf of Mexico into the Eastern United States this morning.  Note that the interaction with the disturbance over the Bahamas has still not occurred but is in the process of interaction just now.  There is clearly a divide in the moisture field between the strong upper level trough and the upper low now over Cuba.  This observation is playing a role in the forecast that I am about to present.

The question for the time period between now and early Sunday morning is what type of mesoscale forcing will develop and what boundaries will unfold as a result.  I have been noticing a trend in the mesoscale model data since last night and into this morning of how the rainfall will develop over the Philadelphia and New York City metropolitan areas today.  The results were rather interesting.

The radar this morning clearly shows the warm front is well to the north of the forecast area.  The air mass we are in is a warm and unstable air mass that will remain in place through this evening.  Weak low level and mid level disturbances are racing from southwest to northeast over the Mid Atlantic and will keep a threat of scattered showers over the entire Philadelphia and New York City metropolitan area through this evening.  Given the moisture in place from the Gulf of Mexico and the high dew points in place (lower to mid 60’s), there is a significant threat that these showers will produce very heavy downpours and may lead to minor flash flooding for the region.    Beware that these showers will rapidly reduce visibility while moving through.

As mentioned earlier the moisture from the disturbance over the Bahamas and Cuba still has not interacted with the trough.  I mentioned last night that this was going to be an important indication for the forecast and it is!  I now believe that the introduction of moisture from that disturbance will happen too late to impact much of the forecast area.  What this means is that two separate areas of heavy rainfall will be moving up the coast and instead of phasing into one large band of heavy rain, there will now be two.  One approaching the region from the west via the cold front and another moving up the coast from the Atlantic.  The two areas of rainfall will interact and phase into a solid line of heavy

rainfall over eastern Long Island, the New Jersey coastal waters, and extreme southern New Jersey.  The NAM-WRF guidance along with some MM5 guidance shows this perfectly.

So what does this mean for the forecast?  Well remember what I always say about mesoscale forcing and interactions.  When air rises in one place, it must sink at another.  I believe there is potential for sinking air ahead of the heavy rain band with the cold front and ahead of the rainfall approaching from the coast.  This sinking air would essentially produce a “dry slot” somewhere over the forecast area, and ironically that dry slot is setting up right over the Bronx for this evening for roughly 3 hours.  Now, I would still suggest that the best motive is to take a NOW-Casting approach for the game, which I expect to do by around 6 PM on this website.

The cold front clears eastern Long Island, Connecticut, and the New Jersey coastal waters by early on Sunday morning.  High pressure will build into the region for Sunday with clearing conditions, lower humidity, and cooler temperatures.

Tags: Albany, alcs game, Allentown, Atlantic City, atlantic city weather, atlantic ocean, Belmar, Bridgeport, canadian maritimes, cape may nj weather, central Pennsylvania, Citi Field, coastal waters, cold front, Connecticut, craigles nyc, current weather in new york, delaware river valley, Freehold, Gulf of Mexico, hail, Hartford, heavy rain, Islip, jackson nj weather, lightning, long beach island nj weather, Long Island, Long Island Sound, Long Island weather, manhattan weather, marine weather nj, mesoscale model, metropolitan areas, Mets, Mid Atlantic weather, model data, negative axis, New Jersey, New Jersey coast, new jersey shore weather, New Jersey snowstorms, New Jersey Weather, New York, New York City, New York City Weather, New York snow storms, New York Weather, new york weather today, Newark, newark nj, newark nj weather, nj local weather, NJ Weather, nj weather 10 day forecast, nj weather forecast, nj weather radar map, nj weather report, noaa, northern Mid Atlantic, northern Mid Atlantic weather, ny weather 10 day, ny weather forecast, ny weather forecast 10 day, ny weather map, nyc weather map, ocean city, ocean city nj, pa weather alerts, pa weather forecast, pa weather map, pa weather radar, pa weather report, past new york weather reports, Pennsylvania, Pennsylvania weather, Philadelphia, philadelphia pa weather, Philadelphia Weather, Phillies, point pleasant nj, Poughkeepsie, pressure gradient, princeton nj weather news 12 nj weather, Reading, satellite image, scattered showers, Scranton, scranton pa weather, seaside nj weather, slow pace, snow, snow storms, strong, Sussex, thunderstorms, tides, tornado, trenton nj weather forecast, upper level trough, water vapor satellite, weather and nyc, weather doylestown pa, weather easton pa, weather edison nj, weather for nyc, weather for pa, weather forecast pa, weather impacts, weather in new york, weather in nj, weather in nj today, weather in ny, weather in nyc, weather in nyc today, weather in pa, weather indiana pa, weather map, weather montclair nj, weather new brunswick nj, weather new york, weather new york city, weather newark nj, weather nyc, weather nyc forecast, weather nyc ny, weather ocean city nj, weather of nj, weather of nyc, weather princeton nj, weather scranton pa, weather union nj, weather wayne nj, western pennsylvania areas, White Plains, widlwood nj, Wild Wood, wild wood nj weather, Winter, winter 2009, winter forecast, winter predictions, winter weather 2009, winter weather advisory, winter weather forecast, winter weather predictions, yahoo weather nyc, Yankee Stadium, Yankees