NY NJ PA Weather Forecasts

A Snowy Thursday In Store For The Forecast Area

9:58 PM

As temperatures crash through Wednesday and into Thursday, an Alberta Clipper will be quickly moving through the southern teir of the Great Lakes and into the Ohio Valley.  By early Thursday morning, this low pressure system will move across southern Pennsylvania and then exit off the coast of southern New Jersey.  The interaction of the warm Atlantic waters with the arctic cold air mass over the land mass will support a signficant thermal gradient along the coast and allow the low pressure system to quickly intensify to the east of New Jersey and just south of Long Island.  The low pressure system will not produce a significant amount of precipitation over the forecast area with the maximum liquid precipitation of up to 0.25″ along the coast.  However, with temperatures in the 10’s and 20’s, the liquid to snow ratio will range from 12/1 to over 25/1 depending on the location and time of the snowfall.  These high ratios will support the potential for snowfall of up to 6 inches in some locations and even an isolated accumulation over 6 inches in areas along the coast where mesoscale banding can form as the low intensifies.  The following map illustrates what I believe are the areas of significant threat.

Description:

Purple:  This area covers coastal Connecticut, all of Long Island, the immediate New York City metro, and coastal central New Jersey.  Snowfall accumulations of 3 to 6 inches are expected with locally higher amounts.  The idea of the forecast is that on Thursday morning, the low pressure system will begin to quickly intensify.  Low and mid level forcing is focused over these locastions to the north and west of the developing low pressure system, which will enhance precipitation in these areas.  There are some indications that a small area of convective precipitation in the coma head of the developing low pressure system may impact this location as well, which may have the potential for slightly higher snowfall totals. 

Blue:  This area covers much of the rest of the forecast area expect the central Hudson Valley and Philadelphia on south.  In this area, the low pressure system will either have not matured enough, with liquid precipitation amounts only supporting a 1 to 3 inch accumulation over these locations.  Later on Thursday morning, parts of south-central New Jersey, the southern Hudson Valley, and northern Connecticut will be just outside the area of best lifting, with snowfall amounts ranging from 1 to 3 inches.

Light Blue:  The track of the low pressure system puts both of these areas in a region of limited lifting and moisture availablity.  For Philadelphia on south including southern New Jersey, the track of the low pressure system will be right over this region with the best lifting to the north.  Although scattered snow showers are expected, only up to an inch of snowfall is expected in this location.

Further to the north, over the central Hudson Valley and near Albany, the lifting and moisture is just too far to the south to produce much of anything but a few snow showers and possibly a dusting.  

Bust Potential:  There are several key elements that would change this forecast.  One being that the low pressure system does not intensify on Thursday morning, which will lead to the entire forecast area only getting 1 to 3 inches save Philadelphia on south where accumulation amounts wouldn’t change much anyway. 

Another bust potential is the storm track.  If there is a shift in either north or south, the best area for dynamics will shift along with it.

A third bust potential is the low pressure moves too fast for the intensification to matter, thus limiting snowfall amounts. 

There are NO concerns about precipitation type with this clipper.   

The best time period for moderate to heavy snowfall will be from 4 AM through 10 AM Thursday.