FROPA
Indicates that a weather front (cold, warm, or occluded) has passed over the station during the observation period. Frontal passages typically bring significant changes in wind direction, temperature, pressure, and cloud cover. Pilots should expect rapid weather changes and possible wind shear near the front.
RMK FROPA
RMK AO2 FROPA PRESFR
RMK FROPA WSHFT 30
FROPA stands for "Frontal Passage" in the remarks section of a METAR report. Indicates that a weather front (cold, warm, or occluded) has passed over the station during the observation period. Frontal passages typically bring significant changes in wind direction, temperature, pressure, and cloud cover. Pilots should expect rapid weather changes and possible wind shear near the front.
FROPA appears in the remarks (RMK) section at the end of a METAR observation. The remarks section follows the main body of the METAR and provides additional details about the observation that don't fit into the standard coded format.
Here is an example: "RMK FROPA". This appears in the remarks section and indicates frontal passage information as part of the weather observation.