The new work week will be getting off to a dry and relatively tranquil start… However, we’re expecting rain around here during midweek, and it will actually be getting started late Tuesday afternoon in most places. Because some vigorous jet stream dynamics will start digging into the eastern third of the country on Wednesday morning. There may even be a few thunderstorms scattered about the area. We feel that, at the very least, rain at some point on Wednesday could be heavy enough to cause flooding, especially of poor-drainage areas, as well as of some streets and highways.
On the current weather map, there’s a cold front located in the Plains, and it’ll be tapping into rich moisture from the Gulf of Mexico late tomorrow, tomorrow night and on Wednesday.
That front shouldn’t manage to reach the Eastern Seaboard until Wednesday evening, and a large zone of high pressure is sitting atop the mid-Atlantic states right now. Because of the placement of that high pressure system, winds are very light and the sky mostly clear early this morning. Therefore, many communities outside of the big, coastal cities are starting off in the upper-20s. Conversely, many urban centers are in the upper-30s.
Despite the cold start, the temperature should at least manage to reach the upper-40s this afternoon. There should be a few thermometers touching 50 (especially in southeastern Pennsylvania, across South Jersey, in Maryland and Delaware). Monday night, as that ridge of high pressure begins to drift to the east, there will be a light, south wind and a few clouds. Both should prevent Monday night from being as cold as this last one, and good enough to keep temperatures from dropping any lower than the lower-30s in the normally colder spots and near 40 in the big cities. Clouds Tuesday will be thickening rather quickly several hundred miles ahead of that cold front.
However, even though the day will turn out rather cloudy, the south wind that will transporting mild and increasingly moist air along the East Coast will allow for the temperature to reach the mid and upper-50s in most places. That corridor of rain associated with the cold front will be arriving late tomorrow (soonest in western locations than in the east), and the negatively-tilted trough axis, or ‘dip in the jet stream’ on Wednesday will cause a wave of low pressure to form near the Delmarva Peninsula. This is the mechanism that will enhance our rainfall tomorrow night into early Wednesday, and those strong jet stream dynamics may help fuel a few potentially heavy and gusty thunderstorms.