Why do weather systems circling high pressure areas produce better weather and tend to be more stable than low pressure systems?

mscorpion

A low pressure system means that the air is rising. As the air rises it cools and forms clouds, often times resulting in wet weather; rain, snow, hail take your pick. the instability in the low pressure system as the direct result of all the moisture that goes into the system, and that moisture has to go somewhere, thus, the instability of the low pressure system. May 11 07, 3:11 PM

gmackematix

Presumably most of us know that wet air rises, cools and condenses into clouds. Why should air swirling into a low pressure area be rising and whirling about more quickly than air swirling out of a high pressure system? And how exactly does "moisture" having to "go somewhere" affect the relative stabilities of these systems (i.e. the tendency for high pressure areas to hang around much longer)? May 12 07, 9:31 PM