The storm that brought substantial rainfall to the Northeast will depart through eastern Canada today, and a high pressure area will take its place. Ahead of the high, tomorrow will be a cool day with northwesterly breezes in New England and the Middle Atlantic states. However, with the high pressure area offshore and another cold front approaching, there will be an increasing southwesterly flow of much warmer air on Thursday. This video shows that sequence of events then proceeds through the coming weekend.
A cold front will approach the I-95 corridor on Thursday night, but computer models show differing ideas on whether it moves right through or instead stalls and prolongs a shower threat into Saturday. It appears the weekend will start on the cool side, but that much warmer air will sweep into the Northeast on Sunday.
However, after the warmup, another cold front will move through the Great Lakes and Northeast with at least some rain. This map contains the forecast for Sunday evening, and includes precipitation predicted for 2 p.m. through 8 p.m. ET.
A storm strengthening off the Middle Atlantic coast will cause episodes of rain and cool gusty winds from Maryland to Maine. The heaviest rain today is focused on the Washington, D.C., to New York City area. Later tonight and tomorrow, the heaviest rain and strongest winds (gusts of 30-40 mph) should spread northeastward across New England. As the storm slowly departs, the weather will improve from southwest to northeast. This map shows the circulation around the storm as of 9 a.m. ET.
The reason for this is a growing and then stalling storm aloft. This map shows the predicted circulation around the storm on Wednesday evening, showing how the moisture could keep going round and round until the storm leaves.
This mornng, showers were moving across the lower Great Lakes region. A band of thunderstorms developed near Chicago before 6:30 a.m. CT and reached the southwest Michigan shoreline an hour later (8:30 a.m. ET). The following maps show the shower zone and Chicago area lightning.
The tropics have been more active recently. This map shows various entities that area being tracked and analyzed. Hurricane Gonzalo stands out clearly.
A couple of days ago, the storm entering the East had a stronger circulation than it does now. Here is the pressure analysis from earlier this morning. Several minor disturbance can be seen, and trough lines representing those have been sketched on the map. Note that there is little difference in temperature from western Pennsylvania to Wisconsin.
The rain band is only 100-200 miles wide, but it is moving slowly. This map shows its location at 10 a.m. today. Once the main rain band passes, it won't be quite as warm as it was when the rain started. However, by mid-October standard, it will still be mild.