The North American jet stream is a wind channel set in the Stratosphere. Along with the Westerlies it blows from West to East across the Northern hemisphere. As storms form over the Pacific ocean these two global winds push the storms across our country starting in California across the plains and finally to the East Coast.
One consequence of this is, due to the slow thermal changes in large bodies of water like the ocean, Western states such as California and Oregon see more stable climates with not very large fluctuations in temperature and humidity. The temperature of the air coming off of the sea tends to keep fairly consistent temperatures once they reach land.
Land however tends to change temperature very quickly in comparison to the oceans. As the global winds push air across the plains and toward the Eastern states the air will heat and cool much more rapidly, creating depressions in pressure that attracts storms and creates much more wild fluctuations in temperature in states such as North Carolina and Pennsylvania.
Strong storms normally do not last in these high temperature fluctuating areas for long and will lose strength across the middle of the country if not destroying themselves completely against the Rocky Mountains.
A jet stream is a long and narrow high speed air current. Generally, it flows in an eastward direction. Meteorologists can make weather predictions based on jet streams. Not only is it important in regards to weather prediction, it is important for the airline industry as well so that airplanes may travel safely.
Jet streams are usually located anywhere from 25,000-48,000 feet above the surface of the Earth and their winds range anywhere from 57 miles per hour to 300 miles per hour.
Basically, storms are pulled in west to east direction because of the strong current of the jet stream.
Jet streams are fast moving, thin bands of air that move around the Earth. Jet streams move in curves from west to east, roughly 6-8 miles above the Earth (toward the area where the troposphere and stratosphere meet). Jet stream winds can reach speeds of 150-250 mph. These strong winds cause changes in precipitation and temperature and determine where weather systems travel. In North America, if the polar jet stream dips south of your location, you will have colder temperatures, and if it rises north of your location, you will experience warmer temperatures.
The Polar front jet stream is important for meteorologists to study because it is where warm and cold air masses come together and can create storms. In North America, our winters typically are colder as the Polar front jet stream moves south, causing colder temperatures to dip lower in the United States.
Another jet stream, the subtropical jet stream, located closer to the equator has less impact on the North America's weather.