You are on a boat in a fiord in Glacier Bay, Alaska. It is a clear sunny day with temperatures near ...

You are on a boat in a fiord in Glacier Bay, Alaska. It is a clear sunny day with temperatures near 20C with no wind.
 
  Within 5 minutes the sky is still clear but the wind is blowing at 30 knots down valley, the sea is filled with whitecaps, and the temperature drops to 5C. What just happened?
  A) You experienced an afternoon sea breeze, blowing cold air off the ocean.
  B) A storm front must have passed.
  C) You experienced a valley wind, caused by cold air spilling off an ice cap down the valley.
  D) You experienced a Chinook wind.