Tuesday 9 a.m.
The upper-air current arriving in Pennsylvania this week originates over the Gulf of Mexico, so it is no surprise the main weather theme is warmer and more humid than typical for the season. However, computer models suggest that on Sunday, the flow reaching Pennsylvania will have originated in western Canada. Translation: warmer, then chillier. This video has more:
The details of the weather pattern are far less clear-cut than the overall trend. For example, there has been rain, some heavy, in a corridor extending from Pennsylvania to Virginia. Pittsburgh has been near the western edge; Philadelphia just east of the eastern edge. Farther south, violent thunderstorms developed in east-central North Carolina. Here is a map showing where precipitation was at 10 a.m. EDT.
This map shows the high pressure area that is promoting cool, dry weather in the Northeast today. The low pressure area on the left side of the map is associated with a cold front that will send showers eastward tomorrow.
With fine weather likely on most of the days ahead through early next week, leaf viewing will be a cool experience for many, especially in areas highlighted on this map showing the typical progression of peak fall colors:
This map is a forecast of the upper air flow early on Saturday, Oct. 16. It shows a mild to warm pattern for the Great Lakes and Northeast. The second map is for two weeks from today. Northern snow showers, anyone?
...with almost 16 inches of rain in Myrtle Beach, South Carolina, and more than 20 inches around Charleston. You don't find amounts like that anywhere in the historic record for this area. This picture shows the radar-estimated rainfall over South Carolina between Friday afternoon and mid morning today:
This map shows where Hurricane Joaquin was just before 8 a.m. ET. You can also see the stripe of clouds centered just of the Middle and North Atlantic coasts.
There are competing forces acting on it, and each move it makes will place it under different influences. This has made it very difficult for computer models and meteorologists to judge where it will actually go. This is reflected in the track model collection on this map: