This video outlines the forecast for the Great Lakes and Northeast from now through early next week.
Meteorologists use a variety of weather maps to study patterns that affect day-to-day or minute-to-minute changes. One map is the 500mb chart. Below are two versions of the same map. One shows a contour interval of 60 meters, which is standard for this kind of map. However, what if you wanted to see more details. You could use a far smaller contour interval, in this case 5 meters (second map). When looked at this way, you can see two distinct flows in the East: one from the south with moisture and one from the west that is dry. There is a problem, however: the model solutions evolve over time, and as we get closer to next Monday afternoon (the time the forecast maps are using), the lines and orientations will probably change.
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.