This level of the atmosphere gives us a very good look at the trough/ridge pattern. We look for long wave troughs and ridges, and also shorter waves. Many times we see these "upper level short waves" riding through the long wave pattern. These disturbances create upper level energy that contributes to rising air motion and the formation of clouds and precipitation. Specifically, we assess the strength of "vorticity" in the atmosphere. Vorticity is the "spin" of something. There are two types. Negative vorticity refers to a clockwise spin, associated with high pressure and ridges. Negative vorticity contributes to sinking air and a drying out of the atmophere. Positive vorticity is a counterclockwise spin, associated with low pressure and troughs. This positive vorticity contributes to rising air, lowering air pressure at the surface, and usually the formation of clouds and precipitation. Notice the upper level low over northern Mississippi, and a long wave trough over the Pacific Northwest with lows and plenty of vorticity from the northern Rockies into North Dakota.