Mate I hope that didn't sound condescending, I'm just putting everything in for completeness so it can be understood.
I wish I could find a diagram to explain it. Now I have to draw a really bad one myself...
The air flowing over the structure (represented by the blue line) has to take a few short cuts where there are flow impediments. These short cuts leave stagnant area's (like the yellow area) where there is little or no flow so the static pressure is higher.