Hi, I teach fifth grade science in Hope Mills, NC. Will the cool air behind a cold front that approaches the warmer air, be a high pressure system?

MIKE MOSS SAYS:     Steve,   Exceptions are possible to almost any generalization in meteorology, but as a rule your statement does work out for our area. When there is a well defined cold front passing through, that front will generally run coincident, or nearly so, with a surface trough of low pressure and just ahead of an upper level trough. Just to the west of the front, surface pressures begin to rise and often lead back to a high pressure center well to our west that will drift eastward and dominate the region for a few days following the frontal passage.  The cold, dry air is part of the reason for the higher pressures, though it is more complicated than that, also related to the three-dimensional flow of air throughout the depth of the atmosphere, and the way in which those flows at various levels converge, diverge, accelerate and decelrate, which un turn leads to areas of upward motion, downward motion, and net buildups or losses of mass over various locations. Where the total mass of air increases in the  column stretching from the surface to the "top" of the atmosphere above a point, surface pressure will increase, and vice versa.