NY NJ PA Weather Forecasts

Major Changes On The Way

Get ready to say good bye to the ridge in the East or at least the sustained ridge in the East. 

A strong cold front supported by a strengthening upper level low and deepening trough will drive through the forecast area on Saturday afternoon.  There is a significant potential for strong to severe thunderstorms with this cold front as the cool, dry Polar air will clash with warm, humid and unstable air mass over the forecast area.  Significant lifting and growing vertical wind shear will support the potential for some strong to severe thunderstorms to develop.  

Once the cold front clears, a deep trough will dig into the eastern two-thirds of the nation.  The upper low over east-central Canada will support strong convergence and confluence over the central and eastern Great Lakes, which will support strong Canadian high pressure over the forecast area.  

While a strong trough is carved out by the northern branch, a disturbance will move into the southern Plains via the Sub Tropical/southern branch of the Polar branch.  The model guidance does not have a strong handle on how the two jet streams will interact.  For example, the ECMWF develops a strong negative NAO structure which slows and suppresses the storm track and produces clear skies and very enjoyable conditions for the region on Tuesday.  Meanwhile, the GFS drives the surface low right into the Ohio Valley with heavy rain for the entire forecast area on Tuesday.

I think that a strong negative NAO/AO structure will develop however I think the ECMWF is on the extreme side.  As a result, I have the low pressure system moving from Mississippi Valley to the Ohio Valley and then redeveloping along the Mid Atlantic coast line.  The strong convergence and confluence should keep high pressure to the north of the forecast area, which will likely lead to a CAD feature to develop.  As the moisture loaded low pressure system tracks towards the forecast area, I think there is potential for frozen precipitation for the interior, especially northeastern Pennsylvania, northwestern New Jersey, the Hudson Valley, and interior Connecticut.  This situation will have to be watched very carefully.  As for the coast line, a heavy rain event can be expected along with some very windy conditions.