場合（ばあい）は is a phrase in Japanese that is often translated to ‘in the event of (A)’, or ‘in the case of (A)’. It can be used with almost any type of word, but will require な when following a な-Adjective, or の when following a noun.

• オートバイに乗（の）る場合（ばあい）はヘルメットをかぶってください。
  In the event that you will ride a motorbike, please wear a helmet.
• 咳（せき）がひどい場合（ばあい）はマスクをしてください。
  In the case that you have a bad cough, please wear a mask.
• 仕事（しごと）が大変（たいへん）な場合（ばあい）は私（わたし）に電話（でんわ）をしてください。
  In the case that your work is difficult, call me.
• 私（わたし）の場合（ばあい）は冬（ふゆ）が好（す）きです。
  In my case, I like winter. (Personally I like winter)

場合（ばあい） by itself is usually translated as ‘case’, or ‘situation’. It is frequently used to highlight a hypothetical situation, or a viewpoint/characteristic of another person.

• 浅草駅（あさくさえき）に行（い）く場合（ばあい）はどの電車（でんしゃ）で行（い）った方（ほう）がいいですか？
  If I were to go to Asakusa station, which train would be the best to take?
• あなたの場合（ばあい）、こういう時（とき）はどうする？
  In a situation like this, what would you do?

When 場合（ばあい）は is highlighting a viewpoint/characteristic of another person, this is almost always in contrast/comparison to something that is already being discussed. This is an example of the contrastive nuance of the は particle.