Most places across the region were spared any additional flooding yesterday, as well as some very potent thunderstorms. But as an upper-level low pressure system, the slow-moving feature which we’ve talked about all week, interacted with daytime heating, a few strong thunderstorm cells did erupt over the mid-Atlantic region. Because of the counter-clockwise rotation of the upper-level winds, these moved from Delaware and eastern Maryland northward into much of eastern Pennsylvania and western/central parts of New Jersey. A severe thunderstorm watch was posted for most of those aforementioned places shortly before 12:30 p.m. (and it ran until 8 p.m.), but the worst aspect of these storms was heavy rain/flooding. Combing through the damage reports, there was a report of one-inch diameter hail in Berks County, PA — but nothing else of significance (no reports of high wind gusts, for example).
Hopefully today, we’ll be able to avoid a situation where showers and a thunderstorm produce any kind of flash flooding, damaging wind gusts or hail. The regional radar mosaic during the pre-dawn hours indicated that a few showers were slowly rotating around the center of circulation, which we have identified as sitting directly atop northeastern Pennsylvania. At the same time yesterday, it was located in the eastern Ohio River Valley. There’s ONE GOOD THING about having plenty of clouds and showers occurring early in the morning across much of eastern Pennsylvania and in upstate New York >> this should tend to keep the atmosphere much more stable for at least a while. Therefore, it would tend to limit any widespread outbreak of convection (including any strong or severe thunderstorms). However, if some breaks in the clouds tend to start showing up after 11 a.m. or lunchtime, then a scenario which would lead to a rapid warming would kick in — and any thunderstorm in the region this afternoon would be capable of producing wind gusts in excess of 58 mph, a drenching downpour and hail. The Storm Prediction Center in Norman, Oklahoma has NOT issued a ‘slight risk’ for severe weather today.
Have a good weekend.