Alrighty, here goes.
After the airport identifier is the time in GMT that the weather reading was taken. SFO's 251856Z is on the 25th day of the current month, at 6:56pm GMT. That'd be 10:56am local time (PST). Winds you already know.
5SM is the visibility in statute miles that you can see the airport. RA is rain. BR is mist. Clouds are next, with few clouds at 1000ft, a ceiling of broken layered clouds at 4200, and overcast clouds at 5000ft.
Temperature/Dewpoint, in Celsius, and Altimeter in inches of mercury.
Wash/Rinse/Repeat for the others.
The other thing that helps, is that the phone numbers for the ATIS for most airports in the US are listed at AirNav. I just gave them a call.