favorable has 5 distinct synonyms spread across 4 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is unfavorable.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
(of winds or weather) tending to promote or facilitate
“the days were fair and the winds were favorable”
presaging or likely to bring good luck or a good outcome
Synonyms, antonyms and the broader and narrower relations for favorable come from Princeton University’s WordNet. Full sources and licences.
“a favorable time to ask for a raise”