My Contractor has included EW’s on his revised programme along with his consideration of the potential effect the notified EW has had. I am arguing that I am happy to show the EW as a milestone but until a CE has been issued on the matter their is no time relation.
I would recommend showing the early warning as an activity, with the actual start date being the date it was raised, and the remaining duration the minimum time it is envisaged that it would take to give an answer to the early warning. If that is then logic linked within the planning software to the activity that it could affect then the float shown on that activity will give an indication (but only an indication) of its urgency.
However, the effect that the early warning might have on subsequent activities should not be shown on the programme, which was why the requirement to show “the effects of notified compensation events” on a revised programme was deleted in the 2006 version of the NEC3 contracts.
A single milestone could be shown - but this would serve little purpose other than a record of when it was raised - hence on a practical basis I would do what I have described in the first paragraph.
If you want to see a “what if” scenario that this could have then by all means it could be plugged into the programme to see, but this should not remain in the programme issued for acceptance as this is not what we know at this stage will happen. The actual forecast effect will be picked up as you say when the event is recognised as a compensation event i.e. known to be happening *(rather than might happen!).
An early warning by its very nature if MIGHT or COULD happen should not yet be affecting planned Completion.