Lightening distant north-northeast. rain began 26 minutes after the last hour. cloud layer flight level 40 visibility 3 below layer 7 above tops of clouds. wind data estimated altimeter setting/sea level pressure estimated. rain shower 3 southeast moving east. maintenance is required on the automated observation system
The FAA does not set the standards for weather observations in the US, the National Weather Service does. The Federal Meteorological Handbook #1 is the guide for surface observations in the US and includes a chapter on remarks.