空が暗いですね。雨が降り___ですよ。
Q. Which suffix expresses 'looks like it's about to rain' (direct observation)?
Translation
The sky is dark. It looks like it's about to rain.
Explanation
Masu-stem + そう expresses an imminent event judged from appearance: 降りそう 'about to rain'. ようだ/みたいだ infer from evidence more generally and attach differently (降るようだ), and らしい reports hearsay.