A poopy day at the airport finds you and your buddies sitting around engaged in a serious session of hangar flying. You decide to amaze the other airport bums with some interesting factoids about METARs and maybe even win a beer bet in the process.
A METAR report ending in A01 or A02 is an automated station. A01 means no precipitation discriminator exists, so precipitation type cannot be reported. A02 means a precipitation discriminator does exist. The absence of A01 or A02 tells you the site is human augmented.
If the pressure is rising at more than 0.06 inches per hour, a PRESRR notation is added. The usual cause is a frontal passage or outflow boundary. As this is associated with a density current, be extra vigilant for low-level wind shear.
In some locations, especially in Europe, CAVOK will be added to indicate ceiling and visibility are OK. The definition for this is no clouds below 5000 feet, no cumulonimbus, visibility more than 10 miles, and no significant weather. The FAA does not authorize its use in the U.S. but the predecessor CAVU for ceiling and visibility unlimited is still in the vernacular.
P0003 indicates the precipitation amount since the last METAR report in hundreds of inches. If the value is P0020 to P0030 or higher, there’s a good chance of some standing water on the runway.
In Europe, you may see colors (RED, BLUE) in the remarks. These are NATO airfield weather color codes. A Google search will bring up exact definitions, but in short RED, AMB, YLO, and GRN are usually associated with IMC.
When you see a $ at the end of the METAR report, the station is flagging itself as needing maintenance. One wonders whether the dollar sign is a bit of intentional humor to indicate maintenance expenses are coming.