Slow-moving storm could lock in rain, cool air for Northeast
A stalled front could lead to days of clouds, rain and cool air across the Northeast, with some areas facing thunderstorms, downpours and even a risk of flash flooding.
This radar looop shows the derecho moving across Indiana, Ohio, Pennsylvania and New York. At least 3 deaths have been reported in Pennsylvania related to the violent storm.
Storms have moved steadily across the country during much of this spring. However, AccuWeather meteorologists say there are signs of an atmospheric traffic jam setting up that can have a profound impact on weather forecasts, including the northeastern United States.
A round of thunderstorms can be locally severe from Thursday to Friday with the potential for high winds, hail, flash flooding and a few tornadoes in the Northeast.
Instead of the front pressing steadily offshore this weekend, it will slow and stall near the Appalachians. That will set the stage for clouds, areas of rain and embedded thunderstorms over a large part of the Northeast, part of the Midwest and the Southeast.
Many areas are likely to experience a thorough soaking, and there is the potential for an inch or more of rain in some locations.
"After Saturday, there is a fork in the road in terms of what that storm may do next and has to do with where and when a storm at the jet stream level of the atmosphere forms," AccuWeather Senior Meteorologist Dave Dombek said.
It could pick up forward speed and dry air will chase clouds and rain offshore over the Atlantic.
This scenario would allow dry and chilly to settle in on Sunday with the risk of frost over the interior of the Northeast Sunday night.
In the second possible scenario, a storm may form in the jet stream level of the atmosphere in the Eastern states. Depending on where that storm forms, it could cause clouds, showers and spotty thunderstorms with chilly air to linger Sunday and perhaps into next week.
The unsettled zone may be in the Ohio Valley and Northeast or it may congregate along the southern Atlantic coast.
"Forecasting exactly where a closed low (jet stream-level storm) will form multiple days out is one of the most challenging aspects of the weather," Dombek said, "But this part of the spring to the early summer is one of the favored times of the year to see it occur."
A lack of weather data from high levels in the atmosphere as opposed to the plethora of ground-level reporting sites issuing weather data may be a contributor.
Weather balloons that carry instruments to measure temperature, humidity, wind and pressure help to fill some of that gap. That data is then fed into various computer models, which are the state-of-the-art tools meteorologists utilize.
If the storm stalls in a specific spot, it could funnel a corridor of moisture from the Gulf and the Atlantic to across a portion of the Southeast coast to the mid-Atlantic next week. Such a rain event might be welcome in terms of brush fire relief, but could also spoil days of outdoor activities and possibly trigger flash flooding.
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