Cold and stormy for the next few weeks

As I discussed in my last post, there is a major pattern change upon us. The storm system that brought clouds, rain, and cool weather to much of the southern Plains into the East is starting to wrap up and lift out to the northeast. The upper level trough will be responsible for one last round of rain for New England on Thursday and Thursday night as low pressure redevelops near the triple point and tracks south of Long Island.

In the wake of this disturbance, the first in a series of Canadian troughs will be diving southward into the Plains. Here's the surface forecast for Thursday morning:

You can see the storm system still affecting the east coast, but draw your attention to the Plains where a very strong cold front is cutting southeastward. Also notice the deep low over Minnesota, and that's right, that is snow in the forecast from North Dakota into Minnesota Thursday through Friday. Winter storm watches have been issued for these areas for accumulations greater than 6 inches! By Friday morning, this cold front will surge forward through the Ohio Valley with as much as a 20 to 25 degree drop in temperature from Thursday afternoon to Friday afternoon.

In the long range, this pattern looks like it will become stable for the next few weeks, as a large blocking ridge over the North Pacific creates cross polar flow, sending reinforcing shots of cold air from Canada into the U.S.

If this were in the winter, we would be talking about a notable arctic outbreak, but because it very early in the season, these shots of cold air get modified as they travel south. For instance, the lack of snowcover allows arctic airmasses to warm as they slide across the still warm ground.