Earlier (Bereishis 7:11), the Torah writes that "all the underwater fountains split open." Why here does the Torah omit the word "all"?
Rashi: HaSh-m deliberately did not shut all of them, leaving some open (such as the hot springs of Teverya 1 ) for the benefit of mankind.
Riva citing Chizkuni: According to the opinion that the Flood did not affect Eretz Yisrael, we must say that even so, springs underneath Eretz Yisrael opened.
Seeing as the rain was only for the first 40 days, what does our verse mean when it writes that "the rain ceased from the heavens"?
Ramban (to 8:4): This means that the residual humidity of the air dried up (causing the waters to subside rapidly), and that there would be no more rain until after they left the Ark.
רש"י: ויכלא-...כמו...לא יכלה ממך: כיצד למד רש"י מ'יכלה' ל'יכלא'?
גור אריה: אין חילוק בלשון בין אל"ף לה"א.