Someone a little while back had some questions about USA Metar codes and what they mean, and what some of the weather phenomena codes meant.Here are two picts that should help a bit...sorry they are not of the highest quality, but should be readable still.

try this ...... http://205.156.54.206/oso/oso1/oso12/document/guide.shtml

Try these from the AIM:http://www1.faa.gov/ATpubs/AIM/Chap7/F0701023.GIFhttp://www1.faa.gov/ATpubs/AIM/Chap7/F0701024.GIFEverything you need to know about weather is here:http://www1.faa.gov/ATpubs/AIM/chap7toc.htm