I had no problem getting to the PA Metadata Main page:http://pasc.met.psu.edu/MESONET/metadata/
From there, every choice returns an "Internal Server Error"
I was able to find http://pasc.met.psu.edu/MESONET/currentdatachoose.html
But it looks like "current data" is from Dec 2-3 2009. Perhaps funding got cut for public access web server?
Too bad, it looks lik it was a great resource.
BUT this page http://www.eol.ucar.edu/projects/hydrometnet/pennsylvania/
has links to lots of PA weather resources. (not all links work though)