@chriswachalCan you create the Point of Origin for a Fireball within an area that you can’t see such as darkness or if you are blind? You don’t need to see the point of origin for a fireball spell. Blow up that darkness!
— Jeremy Crawford (@JeremyECrawford) February 2, 2015
Sage Advice: Fireball is described in Player’s Handbook p.241 or Player’s Basic Rules p.90
The Question reminds me that previous editions specify: A streak flashes from the pointing digit and, unless it impacts upon an obstacle prior to attaining the prescribed range. An early impact results in Fireball.