In the METAR, under the OBSCURATION section for flight visibility, there is a definition for volcanic ash, “VA Volcanic Ash” Currently, Mount Aso in Kumamoto, Japan has erupted, and domestic flights across Japan have been grounded.

500RT: [Eruption of Mt. Aso] Volcanic smoke up to 1000 meters above ground; Kumamoto - The Meteorological Agency calls for attention to damage to crops caused by volcanic ash. pic.twitter.com/P6zour8zJ0 https://t.co/441WP8yufq

— 前田洋輔 (@yokohama_77) November 26, 2014

As you can see, it is indeed marked. Since this is quite rare, I’m making a note of it.

<a href=http://www.aviationweather.gov/adds/tafs/?station_ids=RJFT&std_trans=translated&submit_both=Get+TAFs+and+METARs>RJFT METAR