Many times meteorologist spend large portions of their time talking about and looking at jet streams. When dealing with jet streams, you must think about atmosphere like steps on a ladder. Every step is a different section as you go higher and higher. Each of these sections are separated and looked at in order to better diagnose the atmosphere's current and future state.
In general, there are two major jet streams identified during the forecasting process. The first is the upper jet stream
The upper jet stream exist over 5,000 feet above sea level. It's a section of the atmosphere with fast moving winds in various directions. The directions of these winds when looking at a wider views tell a story. When viewing the upper jet stream, winds displaying an arch typically help identify high pressure systems known as ridges. Many times, ridges signify dry and pleasant weather. A U-shape signifies low pressure systems which allow meteorologist to pay closer attention to identify possible systems displaying different types of precipitation.
When moving down closer to the surface, the lower jet stream is used to mainly identify temperature shifts based off of wind direction along with moisture transportation. Winds originating from the north are typically cooler and drier, while winds from the south usually indicate more moisture and warmer temperatures.