I've no idea who does the TAFS and METAR trends (tempo / becoming etc), but frankly they are very unreliable at times. Fog that is supposed to clear soon but in fact gets worse; snow not forecast, and thunderstorms not predicted or wrongly predicted. MAN does seem to be jinxed at times.
I seem to recall some years ago MAN changed its policy so as not to start snow clearance until the snow has stopped. With moderate or heavy snow, that makes sense as it can be impossible to keep up and ensure safety standards are maintained. The metar reports earlier were showing light snow over a couple of hours and the RVR 1,000m. Perhaps depending whether it's dry powdery precipitation or wet snow, I'd have thought frequent brushing might enable the airfield to stay open or with minimum holding delays. I wonder if the runway had been de-iced. The metars of course are snapshots taken every 30 minutes so I appreciate the degree of snow can vary in between the reports for short periods.