PHILADELPHIA, PA — A tornado warning has been issued in Burlington County as a strong storm system moves through the Delaware Valley and into the Northeast Thursday afternoon. The National Weather Service says the same system is also driving severe thunderstorm warnings and flash flood warnings across parts of Pennsylvania, New Jersey and Delaware.
Forecasters say the main threats are damaging wind gusts, hail and the chance of an isolated tornado. The warnings are expected to stay in place until 7 p.m., and the weather service says conditions could become especially hazardous for commuters and anyone caught on the road during the afternoon surge of storms.
Large hail and 60 mph gusts reported as storms hit Philadelphia suburbs
Trained weather spotters reported quarter- to half-dollar-sized hail and wind gusts as high as 60 mph as the storms moved in. The weather service says those reports match the broader threat from the system, which has a history of producing large hail as it tracks northeast at about 20 to 30 mph.
Locations affected include Philadelphia, Camden, Gloucester City, Cherry Hill and Bensalem. Rapid rainfall and frequent cloud-to-ground lightning are adding to the danger, especially for drivers and people outside as the strongest cells pass through.
The National Weather Service in Mount Holly says scattered severe thunderstorms are possible across the heart of the Delaware Valley Thursday afternoon. That area is being rated a level 2 threat on the agency’s 1-to-5 scale.
Flash flooding concerns spread across urban roads, creeks and low spots
Beyond the wind and hail risk, the weather service says flash flooding is occurring or expected in urban areas, on low-lying roads and near creeks and streams. That means even brief downpours could quickly turn dangerous, especially where drainage is limited or water has nowhere to go.
Heavy rain is also possible in Lancaster and Berks counties as the storm line moves northeast. Severe thunderstorms are expected to keep tracking toward the I-95 corridor, bringing bursts of intense rain along with the chance of more localized flooding.
Officials are advising residents and commuters in the affected area to get to interior rooms on the lowest floor of a building if conditions worsen. The storms are expected to bring the most active weather during the afternoon hours.
Warnings began early Thursday and a few embedded storms could still develop
The first severe thunderstorm warnings were issued between 2:45 p.m. and 3:00 p.m. Thursday, marking an early start to what forecasters see as a fast-moving and changing storm setup. The system is still consolidating off the New Jersey coast, and that means a few embedded thunderstorms remain possible.
The weather service says atmospheric conditions are showing enough spin and shear to support an isolated brief tornado. While that is not the most likely outcome, it is one of the reasons the tornado watch remains in effect for much of the region.
For now, the main concern remains localized damaging winds with occasional hail. The weather service says the strongest storms should continue pushing northeast through the afternoon.
Cold air follows Thursday's storms with Friday highs stuck in the 40s
After the severe weather threat fades, colder air is forecast to move in behind the system, especially Friday and into the weekend. The National Weather Service says highs Friday and Saturday will stay in the 40s, while overnight lows fall into the 20s and 30s.
Snow is possible in the higher elevations of the Pocono Plateau, though less than 1 inch is expected. Most other areas are expected to see rain instead of snow as the colder air settles in.
Wind gusts up to 30 mph are possible Saturday, with the strongest winds expected that day before easing on Sunday. The weather service says frost or freeze advisories may be needed in places where the growing season is still active.
Rain totals vary widely as the system shifts northeast through the weekend
Rainfall north of the Pennsylvania Turnpike to the I-195 corridor is expected to total between 0.50 and 1.25 inches. Areas south of Philadelphia and farther south are forecast to receive less than 0.50 inches, while the southern Delmarva region may end up with less than 0.10 inch.
The storm system is expected to keep moving northeast, with the heaviest rain falling Thursday afternoon before conditions gradually improve. Some warming is forecast early next week, but temperatures are expected to remain below normal for the region.
Even with that slight warmup, highs should stay in the upper 40s to low 50s through the early part of next week. The National Weather Service says the final snow amounts, rainfall totals and any frost or freeze advisories will depend on the storm’s exact track and how temperatures evolve over the weekend.