An adverb used to express probability or conjecture ('probably', 'in all likelihood'); often used when predicting a negative outcome but general-purpose for guesses.
おそらくは明日の試合は雨で中止になるだろう。
The match will probably be canceled due to rain tomorrow.
彼はおそらくは約束を忘れてしまったのだろう。
He has probably forgotten the appointment.
このままだと、おそらくは計画通りにはいかない。
At this rate, it probably won't go according to plan.