what produces (long) gusts and lulls

[jgda]

Mike,
You commented today in your onsite post,"As the pressure gradient goes up the winds should steady out for a few hours until the points and ridges to the west heat up."

How actually does this heating contribute to gusts, and what are the conditions that lead to the long duration lulls/gusts? I can also think of a scenario of mostly no wind but short gusts, but that is less interesting as the former seems to have occurred the last couple days. Thanks!