A weak cool front moved off the Northeast coast last night, and slightly less humid air is coming in behind it. The high pressure area marking the center of the new air mass is moving steadily eastward, and it will be offshore tomorrow. The wind blows clockwise around high pressure areas, so a high off the coast creates a southerly flow of warmer and more humid air. This means it will turn warmer in New England for the end of the week, and temperatures from Washington, D.C., to New York City could reach or exceed 90 degrees Friday and Saturday.
During this time, a cold front will sweep across the middle of the country tomorrow night and Friday, advance through the Great lakes Friday night, then move past the I95 corridor Saturday night. The front will trigger showers and thunderstorms as it slices into the hot, humid air. This video has more.
The pressure analysis on the following map shows the high pressure area responsible for today's sunny and less humid weather in the Northeast. However, you can see that the ridge is rather narrow, and once it moves by, southerly flow will start to bring in more heat and humidity.
Another way to express the outlook:
September is National Piano Month, in tribute to the 20 million people who play the piano to some degree. In the weather department, no real dischord this morning. With sunshine, the temperature will climb up the scale 88. A high pressure nearby will orchestrate sunshine. There is no reason to be flat because you can see sharp. Of course, this arrangement is classic in early September, and it shouldn't really harmony one. However, whenever the temperature does go upscale, you need to keep drinking your coda of fluids. If you overheat, you do have my symphonies, but we are here to help you a choir the info you need to plan your activities.
Later in the week, a cold front will advance across the Plains. The front is one of the keys to the forecast in the Northeast. With such an arrangement, lightning could hit conductors, so the front will be causing showers and thunderstorms when it approaches, but we expect good movement from westerly winds to be clarinet once the front leaves.
Behind the front, the temperature won't drop off a clef, but it will be noticeably cooler and less humid. For now, we descant the possibility of the front stalling. The score calls for more refreshing weather later in the weekend. Of course, we don't fiddle around. If things change, we'll make a concertoed effort to improvise a new forecast so you get information that is up to the minuet.
The cold front is accompanied and preceded by a band of showers, some heavy. As the front continues SE today, some thunderstorms should develop.
Yesterday, there was a sharp boundary between air that was cool and dry enough to suppress thunderstorms and air that was warm and humid enough to support them. This map shows the lightning strikes from 8 a.m. ET yesterday to (almost) the same time today.
As the second low pressure area develops off the East coast, it will work in concert with a high pressure area from Canada to orchestrate cooler-than-usual conditions with showers in the Middle and North Atlantic states Thursday.
Looking ahead to <strong>next</strong> weekend, the Mothers Day Weekend, we see quite a difference between the GFS model and European models on where cold Canadian air is heading at 2 a.m. Sunday.
Rain is spreading across the Middle Atlantic states today. Dampness will linger from southern New York state to Virginia tomorrow even as the main rain area moves offshore.
For the rest of the week and this weekend, the upper-air "steering winds" will be arranged in two separate streams. The northern branch will send air from central Canada toward New England.