I concur with Jet2, delays Saturday morning mainly due to LVP's which did not allow for an immediate recovery in the movement rate following the snow closure.
The Airport snow closed at around 06:30hrs due to 5mm contamination and reduced braking action (Medium), with continuing heavy snowfall. I understand the decision was taken to SNOCLO in an attempt to clear the snow in advance of the morning arrivals peak and prevent further accumulations. Furthermore, I'm told that due to environmental restrictions airports are now required to use 'weaker' anti-icing chemicals which dilute following heavy rainfall or snow. Secondary applications are therefore required to 'top up' the chemicals.
Seems to me that Manchester did a good job given the circumstances - the only other option would have been to continue operating the runway, allow the snow and ice to accumulate and then force a closure during the busiest period.