Hi @Dan8, ah I see where you're coming from.
To my understanding, the MeteoBridge is required unless you want to build your own. Assuming plug and play, I do not think the Apple Airport Express can be used for this as usually, the MeteoBridge would sit between the PWS and your router (i.e. Apple Airport).
However, if you want to keep a computer running 24/7/365 to broadcast the PWS data to your online weather feed, there appear to be some work arounds to avoid needing the MeteoBridge.
I'd recommend reviewing this webpage if you haven't already.
Should you want to explore the 24/7/365 computer setup, let me know and I'll do some additional research on the ins and outs to help point you in the right direction.
Hope this helps.