## 'When you cast a spell' refers to the timing of the use of *Careful Spell*, but probably *not* the forced save

*Careful Spell* says:
> When you cast a spell that forces other creatures to make a saving throw, you can protect some of those creatures from the spell's full force. 

The "when you cast a spell" obviously sets the timing condition for the election of the *Careful Spell*.  That must be chosen, or not, at that time.

What is unclear is whether the "when you cast a spell" timing condition **also** refers to the "that forces other creatures to make a saving throw".

Unfortunately, there are two possible ways to interpret this:

[When you cast a spell]  
(that *forces* other creatures to make a saving throw),  
[you can protect some of those creatures from the spell's full force]  
  
could mean  

>At the point in time in which you cast a certain kind of spell (the kind that forces a saving throw), then you can use your *Careful Spell* to protect those creatures from all future saving throws caused by the force of the spell.   
  
That is, you must elect to use *Careful Spell* at the time of spell casting, but once elected, it will protect a creature for all saves against that particular spell.

**However,**

[When]   
[you cast a spell that *forces* other creatures to make a saving throw],  
[you can protect some of those creatures from the spell's full force] 

could also mean

>At the point in time in which you cast a spell and that spell immediately forces a saving throw, then you can use *Careful Spell* to protect a creature from that immediate saving throw, only.

I believe that the timing condition applies only to *Careful Spell*, not the saves, for two reasons: grammar and the wording of a similar metamagic feature.

## Comparison to *Heightened Spell*

*Heightened Spell*, says (emphasis mine):
>**When you Cast a Spell** that forces a creature to make a saving throw to resist its Effects, you can spend 3 sorcery points to give one target of the spell disadvantage on its **first** saving throw **made against the spell**.

Why specifically call out its *first* saving throw, instead of simply  saying 
>When you Cast a Spell that forces a creature to make a saving throw to resist its Effects, you can spend 3 sorcery points to give one target of the spell disadvantage on its saving throw  
  
If the "when you cast" clause meant that we should count only saving throws made on the turn the spell was cast, then the only reason to indicate its *first* saving throw would be for spells on which more than one save is made by a target *on the turn the spell is cast*.  

On the sorcerer spell list I am counting [just one][3]<sup>1</sup> spell that calls for multiple saves on the turn it is cast, *[Earthquake][5]*, and then only if a target is also concentrating at the time.  

To me, it strains credulity to believe that the 'first saving throw' language was deliberately added to the *Heightened Spell* description so as to cover the effects of just one spell a sorcerer can first get at 15th level.  

On the other hand, it seems very reasonable to me that the 'first saving throw' is meant to apply to sorcerer spells that provoke saves over *multiples turns* or on *subsequent turns*, such as<sup>1</sup> *Blindness/Deafness*, *Gust of Wind*, *Hold Person*, and *Web* all starting at 3rd level, and later on *Fear*, *Sleet Storm*, *Slow*, *Stinking Cloud*, *Confusion*, *Cloudkill*, *Hold Monster*, *Insect Plague*, *Delayed Blast Fireball*, *Incendiary Cloud*, and *Power Word Stun*.

"When you cast" in *Heightened Spell* clearly indicates saves made *on turns after the turn in which the spell is cast*.  Unless you want to argue that  the phrase has different meanings for the different metamagic abilities, "when you cast" should then also allow *Careful Spell* to be used for saves on subsequent turns.  

**Thus, one may protect an ally from *Web* using *Careful Spell* even when the save is not made on the same turn the spell is cast and the metamagic feature is used.**

## Grammar: the feature is describing what kind of spell it works on
The descriptive clause "that forces other creatures to make a saving throw" is *describing* what kind of spell you can use *Careful Spell* on.  You cannot use it on spells which do not force a saving throw (for example, *firebolt*, or *mage hand*).  

If, instead of describing the class of spell, the saving throw clause was *describing the timing condition required*, we would also have to take it literally when it says "forces other *creatures* to make a saving throw".  That is, if making the save was required at the the time of casting, that save would have to be made by more than one creature; you could not use *Careful Spell* on a spell that forced a save for a single creature only at the time of spell-casting.

 
<sup>1</sup><sub>I am currently working from the [SRD][6] and realize that there may be other spells in both categories.  However, I doubt there are many more that provoke two saves for the same creature on the same turn the spell is cast.</sub>
     


  [1]: https://rpg.stackexchange.com/a/47586/23547
  [2]: https://rpg.stackexchange.com/a/47441/23547
  [3]: https://rpg.stackexchange.com/questions/188982/how-does-the-sorcerers-careful-spell-metamagic-interact-with-the-earthquake-spe
  [4]: https://www.dndbeyond.com/spells/prismatic-spray
  [5]: https://www.dndbeyond.com/spells/earthquake
  [6]: https://5thsrd.org/spellcasting/spell_lists/sorcerer_spells/