Tidal information is available from the BBC although this is only for a few days ahead so not so useful for forward planning. Tides are here.
You can get information on tides at Inverness both from the Port Authority when you get there or for some advance warning try the Tourist Information Centre in Inverness.
Inverness Tourist Information Centre:
Castle Wynd, Inverness IV2 3BJ.
Tel: 01463 234353.
Fax: 01463 710609.
I am not sure if they have an email but Visit Scotland does,
Tel: 0845 2255 121 from UK.
Weather of course the BBC and BBC Scotland.
I think you get good Long range Forecasting from a couple of sources, these are the weather outlook and my favourite Weather Online. This site is pretty good in my experience.