Does Flash make a champion untargetable for a moment?

There are some effects in the game which remove a champion's sprite from the map, rendering them untargetable for a moment, such as Elise's Rappel. Does the Summoner Spell Flash do this as well, even just for a split second? Or is the champion always on the field and targettable at all times? In other words, does Flash instantly place the champion at the target location such that there is no moment in time where the champion isn't on the map, or is there a moment when he doesn't exist on the map?

I ask because I was playing a game where I was getting double ulted by both Nunu and Morgana. My Flash was up, but it wasn't enough to escape the range of their ultimates completely. I am wondering whether, if I timed my Flash just right, if I could make myself untargettable for a split second and avoid the effects of one or both of the ultimates when they triggered (i.e., Morgana's stun activated or Nunu's ultimate blew up for tons of damage).

It does not make you untargetable at all, it just moves you instantaneously. The fact that plenty of abilities does not get cancelled by the target flashing is perfect proof of this.

No it does not. It just moves your character ~475 in game. However it does counter a few things;

For example, if you flash while blitz has his fist on you, you will not be pulled (Ezreal's arcane shift does this.) If you flash after naut pulls you, it sometimes negates it. If you flash while Naut uses his ultimate as someone like yi with the ability to be very fast, it will fizzle out after 5 seconds.

It will NOT stop autoattacks though, so if you flash on 2 hp with ashe's auto coming at you, chances are you'll die.