The coldest part of this week's cold snap is now moving into the Midwest and will be over the Northeast tomorrow night and Friday. This video has more, including a look at what could be a major precipitation producer at the beginning of next week.
This map shows the pervasiveness of the northwesterly flow of bitterly cold air behind a cold front that is contributing to snowfall from Washington, D.C., to New York City this morning. Clearing will follow the frontal passage.
In previous winters, I have talked about the upper stratospheric cold signal, where the normal vortex over the North Pole weakens or actually reverses to form a high pressure. That reversal has often been a sign of impending blocking aloft. In blocking patterns, storms are forced south of their usual paths and it often turns colder. This winter, we have seen that such a setup is not required to make it get cold or snowy. The vortex has remained over the pole all winter, and is rooted in place now, as shown on this map from the University of Wyoming.
Looking ahead to late next week, some of the computer models suggest a hurricane could affect areas between the Gulf of Mexico and the Atlantic east of the Bahamas. We are entering the prime part of the Atlantic hurricane season, but at this point there is only one model I am prepared to accept:
The following map shows the individual members of the forecast for the 5,880-meter height line at 500mb. If the 500 mb height is that high, it usually means the weather at the ground in the Northeast is hot. However...
This pressure analysis was made using 9 a.m. ET data. The thin west-east black line is the boundary between hot and cool weather. A low pressure area is moving eastward along the boundary zone, causing showers and thunderstorms. The next low pressure area should send some of the rain farther north.
In the early to middle parts of next week, we expect to see a boundary zone separating hot, humid air to the south from cooler air to the north. A series of ripples or disturbances aloft moving west to east will take turns at enhancing or reducing the chance of showers and thunderstorms.
Looking beyond next week, we see signs of something that has been missing in the Great Lakes and Northeast just about all summer: hot weather. That may change. Here is a computer model prediction of the upper air flow on Sunday, Aug. 24. Note how the flow appears to run from Arizona all the way to north of New England.
The following regional radar map shows that while there are not any large shields of steady rain, there are pockets and bands of rain and thunderstorms that contain heavy precipitation.