If I already mention “there is a chance”, can I still say in the same sentence “chances are”?
Now of course, there is a chance you will ignore the poster, but chances are (most of the time) you will wonder why the poster only has one letter on it.
Yes, of course you may say both in the same sentence.
means there is a high probability something will happen, however, the outcome is not certain, therefore
there is a chance
it may not happen.
You can use the conjunction "but" for opposing outcomes, or "and" for joint outcomes.
There is a chance it will rain today, but chances are it will be sunny.
There is a chance it will rain today, and chances are it will be humid.