How Much Snow Will Cancel A Flight What Are The Chances Of Flights Being Delayed/cencelled In Madrid This Week?

What are the chances of flights being delayed/cencelled in Madrid this week? - how much snow will cancel a flight

I am delighted to go to Granada-Jaén Madrid and Madrid to London (East) Friday 18 December, but I just checked the weather and it seems that the snow expected: (: (: (it's really important that I 's also on those flights that someone knows where it is likely to be canceled flights? do not know how much snow would be necessary to cancel a flight? Even a small amount, which means that it be stopped?
Thank you:)