I'm not an aviator but I do have a significant interest in weather. The simple answer to the question of high/low pressure is to think of the atmos as a sea. It has waves and troughs, some on a very large scale - do a quick search for Rossby waves. Much of the 'turbulence' is generated by transport of associated large air masses from the poles to the equator (or vice versa) as the atmos attempts to moderate its overall temp to an average - cool itself down, effectively.
The Jetstream -broadly- defines a boundary between these polar and equatorial transports. Many low pressure systems are spawned along this boundary and propogate away from it to surrounding areas until they 'fill' with air from surrounding high pressure zones and die out. Some high pressure areas, in contrast to the dynamic LP systems, are relatively static - areas such as the Azores are known for this amongst weather watchers.