8:33 PM

This evening, a cold front is ever so slowly moving through Pennsylvania and will eventually push into eastern Pennsylvania in the next few hours.  A very weak area of low pressure is now over central Pennsylvania and is moving towards the central Hudson Valley.  As the low pressure system moves to the northeast, the cold front and associated heavy rainfall will sink to the southeast and through the Philadelphia and New York City metropolitan areas.

The cold front will begin to produce rainfall over eastern Pennsylvania in the next hour in the form of scattered showers.  Heavier rainfall over south-central Pennsylvania will move towards northeastern Pennsylvania by around 11 PM and continue towards the Hudson Valley and then Connecticut through the early morning of Saturday.  The rest of the forecast area will experience scattered showers, capable of brief heavy downpours.  Rainfall can be expected over western New Jersey by 11 PM, New York City after mid night, and over Long Island by 1 AM.  The cold front will clear the New Jersey coast by 10 AM and Long Island by 12 PM, ending the threat of precipitation for the rest of the afternoon throughout the forecast area.

Strong high pressure will remain in control through Sunday providing dry and somewhat cool conditions for the region for the rest of the weekend.

Model guidance for next week is not showing strong continuity nor agreement between model guidance or even run to run of that model guidance.  The general theme for the model guidance is that a deep trough will be in place from the Rockies to the East coast, while will allow a series of impressive Polar air masses into the eastern two-thirds of the nation.  Disturbances associated with the trough will develop waves of low pressure and one of those disturbances will eventually lead to an interaction of the cool Polar air mass, the moist Sub Tropical Jet Stream, and the warm, unstable air mass over the Bahamas to produce a strong storm over the East coast.  The question of course is which disturbance will ignite this potentially explosive situation.

Overall, I’m expecting a strong coastal low to impact the forecast area towards the end of the week.  The pattern going forward will continue to exhibit a strong upper low over the Aleutian Islands, an impressive ridge over western Canada, and an equally as impressive trough over the Eastern United States.  The question is not if but simply when.