DISCUSSION: As a larger-scale low-pressure system gradually continues to head eastward across portions of southeastern Canada, there will be a continued threat for showers and storms overnight across portions of both coastal and interior sections of the Northeastern United States. This is a direct result of a slow-moving cold front gradually pushing convection along a north-to-south line further east with time during the overnight hours now and on into earlier Saturday morning. Although there is currently only a single flash flood warning effect on the southern flank of this relatively linear area of convection across eastern Pennsylvania, there are still many reports of lightning in the vicinity of this nocturnally-persistent convection and this will be likely to continue due to the continued presence of decent convective instability through the overnight hours. This continued convective instability will be largely due to a persistent flow of warmer and substantially moistened air associated with the more southerly flow pumping northward just ahead of the slowly advancing cold front. Hence, tonight will continue to be a rainy one for many people living across eastern Pennsylvania, southern/central New Jersey, and southeastern New York.
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©2017 Meteorologist Jordan Rabinowitz