This will give you a better understand of the different regions of the USA as told in the National Outlook page.
In the National Forecast, you will see 10 regions.
Northeast, Mid- Atlantic, Southeast, Ohio Valley, Great Lakes, Plains, Rockies, Pacific Northwest, Pacific Southwest, Desert Southwest
The northeast can have a variety of weather conditions. New England (Maine, NH, VT, MA, RI and CT) (north and east of the red line) depending on the weather could be separated from the Northeast Forecast and have its own at times.
The Plains are separated into three sections. Southern Plains, Central Plains and Northern Plains. Each section could have their own forecast or be put together as just the Plains (within the green line)
The Rockies. are separated into three sections. South, central and Northern Rockies. (within the orange line)
There is the Pacific northwest, Southwest and Desert southwest.
The blue line represents gulf states when needed.
Merrimack valley weather 