At 4:02 pm eastern, Fall officially arrived. But parts of the western U.S. will feel more like winter. While in the eastern part of the country, it will be much more summer-like. Why is this? Short answer… the jet-stream. This fast moving river of air, high in the atmosphere, separates colder air to the north, from warmer air to the south. During autumn, the jet-stream can wildly fluctuate in a north-south fashion, causing dramatic temperature swings.
Over the next several days, the jet-stream will dip into the southwestern U.S. This will allow much colder air to pour southward from Canada. This is called a “trough”. But a rise in the jet-stream will take place over the eastern U.S. This “ridge” allows warm air to travel northward. This results in below average temps in the west, and above average temps in the east.
In the west, temps in places like Denver will drop from the 80’s on Friday, into the 50’s by Sunday. And snow will accumulate in parts of the northern Rocky Mountains.
Temperatures in the east will be much warmer than usual. And many cities may see record high temperatures. Chicago, Detroit, and New York City could all see record high temps.
So while the calendar may say that it’s officially autumn, the jet-stream will make it feel more like winter or summer. Welcome to the changing of seasons!
For WeatherNation: Meteorologist Matt Monroe