Is this homebrew spell balanced?

Wind Wave

1st-level evocation

Casting Time: 1 action
Range: Self (15-foot cone)
Components: V, S
Duration: Instantaneous

A wave of powerful air sweeps out from you. Each creature in a 15-foot cone originating from you must make a Strength saving throw. On a failed save, a creature takes 2d8 bludgeoning damage and is pushed 10 feet away from you if a creature fails the save by 5 or more they are knocked prone.

On a successful save, the creature takes half as much damage and isn't pushed.

In addition, unsecured objects that are completely within the area of effect are automatically pushed 10 feet away from you by the spell's effect.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d8 for each slot level above 1st.

Pretty darn close!

First of all, I like this spell. It's a nice combination of damage, battlefield control, and defense. It also is mechanically similar to two existing first level spells: Thunderwave and Burning Hands. And in most ways, it's analogous to them in power and effectiveness.

The one issue I see a potential problem with is the ability to knock multiple enemies prone. If you pull this off and several of your allies have turns before your enemies, you're guaranteeing advantage on melee attacks. That's a bit powerful for a first level spell that also does damage, especially considering the fact that some very common low level enemies that group together (e.g. goblins, kobolds) tend to have abysmal strength scores. Add this to the fact that neither Thunderwave nor Burning Hands create analogous status effects, and you've got a spell that's got a bit too much "bang for your buck."

I'd suggest that the "prone" element be given as part of the upcasting. Specifically, if this spell is cast with a 3rd level spell slot or higher, then creatures that fail the saving throw are also knocked prone (in addition to the increase in damage). At that point, I think this spell will be ready to go!

This is imbalanced, by the simple virtue of being an objectively better version of thunderwave.

• The saving throw targets Strength rather than Constitution, a much rarer saving throw.




• The damage type is magical bludgeoning, which almost nothing is resistant to, as opposed to thunder, which is still one of the more rarely resisted energy types, but nowhere close to as rarely resisted as magical bludgeoning.




• This has the additional effect of knocking prone creatures who fail their save by 5 or more.




• The only difference that isn't definitively superior to thunderwave is that the range is a 15-foot cone rather than a 15-foot cube. This has benefits and drawbacks, and would normally make this an interesting alternative to thunderwave, but with everything else this spell has going for it there's no reason to ever use thunderwave.

It's also worth noting that, as written, this spell is likely to cause arguments about whether it counts as "strong wind" and can therefore be used to disperse fog cloud, cloudkill, and the like. If it can, that's one more way in which it's better than thunderwave, and it also steps on the toes of gust of wind more than a little. If it can't, that's fine, but it's likely to make players unhappy when they try to use it that way.

Many creatures have very high strength scores so a wide variety of creatures will have good saves even without proficiency bonus. Because the prone condition is considered excellent by some people, and wind is generally less deadly than lightning, you may try reducing the damage dice category to d6s instead of d8s.