The concepts learned in this section allow us to understand weather maps. Often, we get a few days of consistent weather, followed by 1-2 days of precipitation, followed by another few days of consistent weather. These are called source regions . The characteristics of the air mass is determined by the characteristics of the surface. Air masses are typically formed when a high pressure cell sits over such a region a week or more, allowing for a stable air mass to remain in the same place.
Fronts are a few miles, or tens of miles, wide.
Within the frontal zone we have mixing of the air masses. Also, typically there is also a steep humidity gradient. Eventually rain occurs, may not be very heavy but may last a few days. After a warm front has passed, the temperature is higher than before the front arrived. The precipitation doesn t last as long as with warm fronts, but may be more violent.