No, the foretelling rolls are not an ability check, saving throw, nor attack roll
The Portent feature says:
When you finish a long rest, roll two d20s and record the numbers rolled.
— Player's Handbook, p. 116
While similar to ability checks, saving throws and attack rolls in that you roll a d20, and used for those later, making this roll is none of those. You are just rolling a d20.
Barding inspiration can only be used on ability checks, attack rolls, or saving throws:
[...] the creature can roll the die and add the number rolled to one ability check, attack roll, or saving throw it makes.
— Player's Handbook, p. 53
Since rolling those foretelling rolls are not one of those roll types, Bardic Inspiration can't be added at that time. They can however be used when the foretelling rolls are used (ie. used as a roll by a creature). See: Can Bardic Inspiration be used on a roll replaced by Portent?