As far as I know in the UK, RMK in a METAR or it may just be TREND.....?, or commonly referred to as a landing forecast can only be issued if a qualified Met man is present at the time of compiling the METAR. I know a TREND is a general forecast trend for the next 2 hrs. If only a observer that is not a qualified Met man is present then no TREND can be issued as the METAR is really an observation and not a forecast.
Again I’m not sure if the RMK would be the same as a TREND in needing a qualified Met man……..?