|Hour 192 of the 12z ECMWF|
The ECMWF is forecasting a strong disturbance to drop down into the northern Plains in mid-September, as depicted above. The 540 line on the upper right image is dipping down into the Northern Plains. The 540 line is commonly referred to as the rain/snow line, with snow being north of the 540 line. That said, if precipitation were ongoing in the northern Plains and this verified, some very early snow may fall in North Dakota/Minnesota.
After the system dips into the US, it will become closed off, and its cold pool will rotate around the western side of the storm. As it closes off, it will rapidly strengthen over south central Canada. This will likely produce some windy weather in the southern Canada and northern Plains regions, and cool air should continue to flow around the regions mentioned.
This is just one of a few signs being seen that show winter is inching closer to our region.