ATIS
The ATIS can be disruptive to all concerned. ATC has to create it to accurately catch prevailing conditions. If these are changing rapidly you'll approximate and generally we will be pessimistic if it is done manually. That is, post the worst case scenario.
Accepted practice though is that the ATIS should be left in general to capture the METAR conditions and that is what is transmitted. We do at times conflict with MET and time permitting will manually scribe the differences. This over-rides the METAR.
There are laid down criteria for when and ATIS must be updated, but if there are only minor variations, the aim to minimise workload in ensuring everyone is on the current information and minimise the R/T loading, is to limit the updates to hourly where ever possible.
For arrivals on first contact with TWR, all traffic will be given an update on conditions that vary with the ATIS. As you can imagine if there is a CB active and it is moving, to keep this type of information precisely updated is not realistic. So reality is to post a generalisation and any significant detail on APP or TWR frequency as it occurs.