A girl stood with the palms of her hands open, checking to see if it was raining.
A girl stood with her palms facing up to see if she could feel the rain on her hands.
1) A girl stood with the palms of her hands open, checking to see if it was raining.
「少女は手のひらを上に向け、雨が降っているか確かめた。」
2) A girl stood with her palms facing up to see if she could feel the rain on her hands.
「少女は手のひらを上に向け、雨を手のひらで感じられるか確かめた。」
「手のひらを上に向ける」は
with the palms (of her hands) open
with her palms facing up
などと言えます。
palm だけで「手のひら」という意味があるので、of her hands はあってもなくても良いです。
ご参考になれば幸いです！
日本 
