ばあい

“In the case of”
Noun +の場合は
Adjective/plain form verb +場合は
な adjective ＋な場合は

場合 (ばあい)  is just a noun that means “case” as in “in the case of”. It’s meaning is very similar to なら and とき. It is almost always going to appear as 場合は.

It can be used in the past tense (completion tense), in which case it functions like たら:

• 鍵をなくした場合は連絡してください – Please contact us if you loose (have lost) your key.
• 試験に来なかった場合は不合格になる – If you (don’t) didn’t come to the test, you’ll fail. 
• 盗まれたばあいは仕方ない。 – If it was stolen, then there’s nothing we can do. 

In the non-past tense, its more similar to なら or 時 (at that time)

• 学校に行く場合は、車が一番はやい.  – If you’re going to the school, its fastest by car. 
• 彼が犯人の場合は、逮捕する – If he’s the criminal, we’ll arrest him. 
• 家事の場合はすみやかに逃げてください – In the event of a fire (at the time), please run away quickly. 

Past and Non past comparison

Past and Non past are similar, but differ in whether the action has been completed.

• パスワードを忘れる場合は ✖- If you know you will forget/will forget/keep forgetting
• パスワードを忘れた場合は 〇- If you have forgotten your password. 
• パスワードを忘れている場合は 〇 – If you have currently forgot your password
  
  
• ひなんした場合は 〇 – If you have evacuated
• ひなんする場合は 〇 – If you are going to evacuate

ばわい

場合, although written ばあい, is usually read as ばわい。Its a rare thing that sometimes happens to double ああ sounds in Japanese. It really only happens with this word. So if you hear it, just know you aren’t crazy.