Lightroom :: How To Sync Changes To Images Over Multiple Drives

I keep my photos on two main drives: one archival drive which is the main storage for ALL my images and lives in my studio, and one that is my portable working drive which travels with me wherever I go. Using Lightroom 3, I import images during a shoot onto the portable drive, and then later I copy the images using Finder to the main archival drive. I don't do the copy while importing from my card because I don't have the time to wait during the shoot. Since I carry the portable drive with me, I make metadata and develop and other changes to the images from a particular shoot in Lightroom, all of which are saved to that portable drive.

My question is, is there a way to have Lightroom sync these changes over multiple hard drives? In other words, how do I sync all the changes I made to the images on my portable drive with the images I previously copied to my archival drive? If I make develop, metadata, and keyword changes to the images in a folder on my portable drive, the idea of having to do it all over again for the same folder on my archival drive seems intensely ponderous, and the idea of copying all the files again every time I make changes seems very time-consuming. Lightroom is so brilliant in so many ways, I'm hoping this is something it knows how to do as well.
 
To explain, the portable hard drive is a small USB powered drive that I can have with me at my day job or take with me to shoots, where I might find time to rate images, make develop settings, add keywords, etc. It's not possible to bring the archival drive with me everywhere, which means I work from the portable drive quite a bit. But I need for the archival drive to be in sync with the portable drive as much as possible, for obvious backup reasons.