Typical Circulation MET

In a low pressure, air is generally coming together at the surface, rising, then separating out again when it reaches the tropopause (or a stable layer.) In a high pressure, the opposite happens: it comes together at altitude, sinks and spreads out when it hits the surface. This has enormous implications, as the rising air in a low will cool, giving clouds and all their effects, whereas in a high the sinking, warming air means vapour will never condense, giving no clouds and more settled conditions.