Thursday 9:30 a.m.
The dreariness of yesterday morning in the Northeast has been replaced by dazzling sunshine and deep blue skies. A fast-moving cold front will send clouds streaming across the Great Lakes then New York and New England today and tonight, then a large high pressure area from western Canada will move for the start of the weekend. You can see and hear what this high pressure area should do in this video, along with what the flow behind it should accomplish later in the weekend.
In the short burst of cold air into the eastern Great Lakes tomorrow, showers will break out in the same areas that had them last night and this morning. Since this air mass is a little colder, snow showers are likely over the higher terrain southeast of Lake Ontario. Snow showers with lightning and thunder hit the Tug Hill Plateau last night, and the same thing can happen late tonight or tomorrow morning.
Severe thunderstorms are likely to break out in the middle of the country late tomorrow and tomorrow night, then rain and thunderstorms will advance into the Great Lakes for Saturday. A switch to a southwesterly flow aloft should keep the moisture mostly north of the Middle Atlantic states for much of Sunday... but as a cold front swings around a few showers should reach the area from southern New York to Virginia on Monday.
In most of the Northeast, it is a dazzling day, with the bright sun playing off the leaves that change hue by the day. It's quite a contrast from the dull dreariness much of the region experienced the first half of the week.
One concern: the chance of cold frontal snow squalls that could move all the way to the East Coast tomorrow night. Sudden snow squalls have been implicated in chain reaction collisions that turn deadly and damaging.
These two maps show the change from the very, very cold flow likely this Saturday to the much milder Pacific-origin westerly flow later next week.
When we look more closely, we see a variety of disturbances embedded in the main current, each capable of temporarily increasing or cutting off the chance of snow. This map shows the setup:
This map shows the circulation around the offshore storm and a larger but less intense storm moving into the Great Lakes. With this sprawling storm likely to be in the region for several days, the weather can vary widely.
...speculation about a snowstorm Monday or Tuesday, and one is still possible. However, timing and placement remain elusive. This map shows the GFS ensemble mean "solution" for Tuesday morning showing snow just off the New England coast. Watch this story evolve on accuweather.com all weekend.