NY NJ PA Weather Forecasts

A Back Door Cold Front That Means Business

7:14 AM

While many think of Spring as a time of green grass returning, warmer temperatures, and a quieter weather pattern; Spring also means the return for the difficult forecast phenomena of a back door cold front.  A back door cold front is basically a cold front the develops over the Canadian Maritimes and drives southwestward through New England and over the Mid Atlantic.  These cold front bring overcast conditions, much cooler temperatures, and sometimes heavy rainfall.  

Model guidance coming into agreement with the idea of a rather strong back door cold front impacting the forecast area with the ECMWF continuing to remain the most aggressive of model guidance.  I like the ECMWF the best for this situation because the model guidance gives the negative EPO pattern a bit more influence on the overall pattern over eastern Canada than the GFS and the ECMWF is closely supported by GEFS and other ensemble guidance.  Once again, it is fun to point out that a trough in the Japan Sea today can impact the forecast over the forecast area seven days later!  

Anyway, on to the forecast!

A strong Polar high pressure system with some moderation from Pacific influences will move from the northern Plains through the forecast area on Friday and Saturday, providing clear skies and slightly below normal temperatures.  I’m going slightly above MOS guidance for parts of the Philadelphia and New York City metro away from the coast due to the influence of the March sun.  With sun angle increasing, I think some locations will break into the lower 50’s. 

The high pressure system will move to the south and east of the forecast area on Sunday, however trouble begins to brew over the Canadian Maritimes.  A strong upper low will develop over eastern Quebec and Labador, which will produce a north to northwesterly flow at 500 MB over the forecast area.  A cold front will begin to develop and drive southward through New England and into the forecast area by Sunday afternoon.  This cold front will have the most impact on the region over the Hudson Valley, Connecticut, and Long Island with increasing clouds and a few scattered showers.  Winds will back from the southwest to northeast behind the cold front and temperatures will fall into the 40’s.  

The cold front will continue to progress southwestward through the forecast area on Sunday night and Monday with broken to overcast skies, a few scattered showers, and much cooler temperatures.  There is a question of just how far southward the back door cold front will get, which is a typical forecasting problem with these type of cold fronts several days out.  Locations ahead of the cold front will warm nicely into the upper 50’s and lower 60’s with clear skies, while locations behind the cold front will have partly cloudy to overcast skies and temperatures generally in the upper 40’s, especially along the immediate coast.  So naturally, the exact location and strength of the cold front is going to be key for the forecast on Monday.

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