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.
It does look warmer for the weekend, but every time the warm air tries to extend into New England it gets chopped down. There could be more showers at times Sunday and early next week as forest we can tell. If any forecast gives you a headache, why not take a friend's advice: Take two aspen; sequoia in the morning.
This map from 5AM ET shows the cold front that is continuing toward this Northeast and Middle Atlantic states. Temperatures stayed up in the 70s all night ahead of the front but it turned noticeably cooler after the front moved through.
The cold front that will cut off the heat will generate strong gusty thunderstorms as it moves southeastward today. The National Weather Service Storm Prediction Center highlights the most likely area for these severe thunderstorms today and tonight.
As the high pressure area in the Northeast moves away, the the southwesterly flow pattern will shift eastward. This means Wednesday could be the hottest day of the week from D.C. to Boston. A cold front will follow.
This is a satellite picture showing rather tame conditions off the South Atlantic coast at 7:45 AM ET today. The area is being watched for any signs of storm development.
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.