'Forecast' was introduced in the Ravnica block, it is a word that represents a group of abilities all requiring a mana cost and the showing of the card from your hand.

702.54. Forecast

• 702.54a. A forecast ability is a special kind of activated ability that can be activated only from a player's hand. It's written "Forecast -- [Activated ability]."
• 702.54b. A forecast ability may be activated only during the upkeep step of the card's owner and only once each turn. The controller of the forecast ability reveals the card with that ability from his or her hand as the ability is activated. That player plays with that card revealed in his or her hand until it leaves the player's hand or until a step or phase that isn't an upkeep step begins, whichever comes first.

Translation:

• 702.54a. - This is the rules text that notes the card must be in your hand to use the ability.
• 702.54b. - Only use it once and during your upkeep. The card remains revealed until it is played, is put anywhere other than the hand, or the game moves out of that upkeep step.