Doppler radar oddity question

[Demon-Xanth]

Inspired by the thread about DC being screwed, I've noticed on the NWS Doppler map there is always a rather strong appearing mini-cell south of Fairfield regardless of what the weather there is actually like:
http://radar.weather.gov/radar.php?rid=dax&product=N0R&overlay=11101111&loop=no

What's happening here that makes the radar so consistently messed up?

 

[Gibsons]

It's the smug from San Francisco.

 

[SunnyD]

California.

 

[PottedMeat]

it's to hide the ufo, dumbass.

 

[CallMeJoe]

Google "radar ground clutter"...

 

[Auggie]

Doppler radar works by analyzing the "scatter" produced when electromagnetic waves hit things. As opposed to a stealth aircraft that has sharp angles and absorbs or linearly reflects radar waves, there are numerous things on the ground in the area of a Doppler cell that have rounded edges and stick up into the plane of waves that the Doppler is sending out and analyzing the bounce-back from. It often can't distinguish rainfall from things on the ground.