A bit more sun Wednesday afternoon than previously expected. In the afternoon there will be sun with some clouds, which would not develop until peak daytime heating. It does not look like there will be any threat for thunder through the morning hours. Rainfall will move in around the 3 a.m. time frame.
As an upper-level low pressure system continues to spin over east-central Canada early Wednesday morning, a very broad trough (or “dip in the jet stream”) remains carved out over the eastern third of the United States — and while it should begin to weaken over the next 24 hours, it still will be capable of causing some widely separated showers Wednesday afternoon.
Most of these will occur across northeastern Pennsylvania, upstate New York, northern New Jersey and New England, because these are all places which will be located to the source of colder-than-normal air aloft.
We feel Baltimore will be too far south of this general area that will encounter any afternoon shower activity.
There will be a transition taking place Wednesday night as the influence of that upper-level feature to the north begins to loosen its grip. But the focus of our attention will then be turning to the south and west.
Here, we’ll be monitoring the progress of both a warm front and a wave of low pressure that will be cruising across the Ohio Valley Wednesday night before it reaches areas east of the Appalachians Thursday.
Clouds should begin to increase around here Wednesday evening, and it will probably also start to rain by early Thursday morning (before 5 a.m.). Most low temperatures will be in the 40s Wednesday night, and then we’re going to see the surface winds shift to the south Thursday. This will cause clouds to thicken very quickly, and showers will follow.
Because a warm front will be the catalyst that will be causing these showers, the temperature forecast will be a little “tricky.” lt will probably just “rain for a few hours” Thursday morning before the precipitation tapers to a couple of showers in the afternoon, and a thunderstorm also cannot be ruled out.
Temperatures, because of the clouds and the early rain, will probably be no higher than the lower 70s, at best.