A major rain storm is starting to move into New Jersey this morning that will promise to produce rainfall amounts of two to four inches throughout many locations in the region, which will lead to wide spread threats for significant flash flooding.
The first primary low pressure system is currently located in Ohio this morning, however a new area of low pressure will continue to develop over central Virginia and move north-northwest towards Lake Ontario and the St. Lawrence River Valley through tomorrow afternoon. As this second low pressure system intensifies and moves north-northwest over the next 24 to 30 hours, a large band of moderate to very heavy rain will pivot from the south to north orientation this morning to a southeast to northwest orientate by this afternoon. This band of heavy rain will slowly move northeast through the Philadelphia and New York City metropolitan areas with very heavy rainfall and sustained winds from the southeast around 15 to 30 mph with gusts over 40 mph, especially in heavy downpours. The rain will end from southwest to northeast starting tomorrow morning over the Philadelphia metropolitan areas and by tomorrow afternoon for the New York City metropolitan areas.
With rainfall amounts of two to four inches over much of eastern Pennsylvania, New Jersey, much of southeastern New York and western Connecticut and one to two inches over eastern Connecticut and eastern Long Island, flash flooding will become a significant problem around river basins and in poorly drained urban locations. I am especially concerned about the Delaware River Valley and much of northern New Jersey were rivers are already at or above flood stage. This rainfall and the rainfall up stream will lead to moderate to major flooding in many of these locations.
The low pressure system and the associated frontal boundary will continue to lift northeast through tomorrow afternoon with clearing skies behind the front and windy conditions from the west and northwest around 10 to 20 mph with gusts over 40 mph at times. High pressure will take hold by tomorrow night with clearing skies throughout the region.
High pressure will be in control through this weekend and into the middle of next week. A few disturbances may produce an isolated rain or snow shower on Saturday night into Sunday morning, however most locations will remain dry. Otherwise, temperatures will be near normal through much of the period, warming to above normal by the middle to end of next week.
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