NY NJ PA Weather Forecasts

Very Heavy Rains On The Way

This week is certainly going to end on the very wet side as a storm gets it’s act together over the eastern third of the nation through Saturday morning.

I’m going to jump right to Thursday afternoon.  The most interesting aspect of this period is the small yet intense southern branch disturbance that moves from the Gulf Coast to the Mid Atlantic by Saturday afternoon.  I’m rather suspicious of this disturbance and I still think this disturbance will force weak cyclogenesis along the coast if not enhance the rainfall over the forecast area on Saturday morning.  

This heavy rain event though is going to be driven by two important features.  The first will be the impressive intensification of the jet maximum at 250 MB, which will be oriented from the Gulf of Mexico towards New England.  A combination of deep layer moisture and impressive upper level divergence will support strong lifting over the forecast area, especially over eastern Pennsylvania through the Hudson Valley.  The second feature is the impressive thermal gradient from ahead of the cold front to behind the cold front.  The thermal gradient reaches a peak on Saturday morning with a gradient of 10 degrees C at 850 MB as the cold front approaches.  This type of gradient will produce a significant amount of low level forcing, which will also support heavy rainfall over the forecast area.  

The combination of significant moisture from the Gulf of Mexico combined with strong upper level divergence, supportive jet dynamics, mid level forcing, and low level forcing all points to heavy precipitation for Thursday evening through Saturday morning.  Rainfall amounts by the end of Saturday will range from 1 to 2 inches with locally higher amounts.