There are several synonyms one could use for the phrase "appear probable." Some options include: seem likely, suggest plausibility, indicate feasibility, exhibit possibility, demonstrate likelihood, and present potential. These phrases can all be used in similar context to convey the idea that something appears to be likely or possible based on the information at hand. Choosing the right synonym can depend on the tone and context of the sentence, but each of these options can help to add variety and clarity to your writing.