Not only do you have to clear the runway and get an acceptable post sweep braking action, you also have to clear the taxiway system, the stands, do the roadways around the stands and the footpaths to/from the tinminal.
Sky Wave, where exactly do the airport find the staff to achieve this? The fire station are mostly involved with clearing the runway/taxiway, then have to go back to the station in readiness for a re-opening, otherwise there is a resultant reduction in fire cover. Baggage handlers once helped with keeping the tinminal infrastructure cleared, but HM Govt outlawed airport operators from shifting bags. These staff are now employed by handling agents so are unable to directly assist?
If snow continues to fall, the swept areas start to cover once more whilst movements occur.
Being stuck right on top of a hill, drifting is an additional issue.
When I started work at Luton in Dec 1981, I didn't witness an aircraft movement for the first 5 days due to the severe snow, so little has really changed. Funny how my memory has faded, as I do not recall Monarch or Britannia slapping a compo bill under the Town Hall doormat?
The 'snow' story was a nice bit of free publicity for easyJet though!