The weather discussions in the last few weeks have featured the term “trough”. What is it? In meteorology, a trough is an elongated area of relatively low atmospheric pressure; the opposite of a ridge. When there is a ridge in the west and a trough in the Central Plains, we often see incursions of cold Arctic air. This may also be combined with one or more surface low pressure systems that bring unsettled weather and increased chances of precipitation. A low pressure system exiting from the desert Southwest can bring Gulf moisture into the Plains, giving us some of our highest chances of winter precipitation.
Mary Knapp, Weather Data Library